Chinese national bird

Chinese national bird

I had the pleasure of collaborating with a fantastic team of individuals on my travels. These individuals included Jiaying Yang, Ye Zhang, Lei Yang, Xiyan Li, Hong Bo, Jia Liu, Min Tan, Wenfei Zhu, Yuelong Shu, and Dayan Wang. Working with them was a highlight of my journey, and I was grateful for the opportunity to learn from each of them.

During my travels, I had the pleasure of collaborating with a team of esteemed researchers and public health professionals, each of whom brought their unique skills and expertise to our shared work. The team included individuals from the Chinese Center for Disease Control and Prevention’s Key Laboratory for Medical Virology in Beijing, such as Jiaying Yang, Ye Zhang, Lei Yang, Xiyan Li, Hong Bo, Jia Liu, Min Tan, Wenfei Zhu, and Dayan Wang. We were also joined by colleagues from the School of Public Health in Shenzhen, including Jiaying Yang and Yuelong Shu, as well as Yuelong Shu from the Institute of Pathogen Biology of Chinese Academy of Medical Science/Peking Union Medical College in Beijing. Together, we formed a strong and capable team, united in our commitment to advancing public health research and practice.

Abstract

As a travelling photographer and bird enthusiast, I had the unique opportunity to witness the ongoing evolution of avian influenza viruses (AIVs) of subtype H3 in China. This evolution, coupled with the emergence of human infection with AIV subtype H3N8, highlights the significant threat that these viruses pose to public health.

During my travels in China from 2009 to 2022, I worked with a team to conduct surveillance in poultry-associated environments, resulting in the isolation and sequencing of 188 H3 AIVs. Through large-scale sequence analysis with publicly available data, we were able to identify four sublineages of H3 AIVs that were established in domestic ducks in China, likely through multiple introductions from wild birds from Eurasia.

Our full-genome analysis revealed 126 distinct genotypes of H3 AIVs, with the H3N2 G23 genotype being the most prevalent in recent years. However, we also identified H3N8 G25 viruses that had spilled over from birds to humans, likely generated through reassortment between H3N2 G23, wild bird H3N8, and poultry H9N2 prior to February 2021.

We also observed occasional mammal-adapted and drug-resistance substitutions in H3 AIVs, highlighting the importance of ongoing surveillance for these viruses and risk assessment to prepare for potential pandemics. It was an incredible experience to be a part of this work and contribute to the understanding of the evolution and potential impact of H3 AIVs on public health.

As a travelling photographer with an interest in bird populations, I’ve learned that avian influenza viruses (AIVs) of subtype H3 are highly prevalent among waterfowl worldwide. These viruses are generally asymptomatic in birds or cause only mild illness (1-5), but they have the potential for cross-species transmission and have been known to cause epidemics in other animal species, including horses, dogs, seals, and pigs (6-9).

Interestingly, H3 AIV played a pivotal role in the 1968 human influenza (H3N2) pandemic. Specifically, the H3 AIV contributed its hemagglutinin (HA) gene to the pandemic virus, although it is still unclear whether an intermediate host was involved (10). This highlights the significant potential of H3 AIV to impact human health and the importance of continued surveillance and research into these viruses. As a travelling photographer, I’m grateful to have learned more about the complex and fascinating relationships between avian influenza viruses and their impact on public health.

As a travelling photographer with an interest in public health, I was alarmed to learn about the recent cases of human infection with avian influenza viruses (AIVs) of subtype H3N8. In April 2022, the first case was reported in a 4-year-old boy whose family raised chickens and silky fowls in Henan Province, China (11). The patient experienced severe symptoms, including recurrent fever and severe pneumonia.

Just a month later, in May 2022, a second case of H3N8 infection was identified in a 5-year-old boy who had visited a live poultry market (LPM) in Hunan Province, China (12). While this patient exhibited only mild influenza symptoms, the two cases combined raised serious concerns about the potential public health threat posed by H3N8 AIVs (13).

As a traveller and photographer, I understand the importance of international collaboration in identifying and monitoring potential public health threats. These recent cases of human H3N8 AIV infection underscore the need for ongoing surveillance and research into avian influenza viruses and their potential to cross species barriers and cause illness in humans. I hope that increased attention and resources can be directed towards understanding and mitigating the risks of these viruses, both for the sake of human health and for the preservation of bird populations worldwide.

H3 avian influenza viruses (AIVs) have been actively circulating in both domestic and wild birds throughout various regions in China. These H3 AIVs have been observed to combine with multiple neuraminidase (NA) subtypes, with H3N2 and H3N8 being the most common ones. Phylogenetically, these viruses belong to the Eurasian lineage that is found in wild birds across the Eurasian continent. Reassortment events between different subtypes of AIVs frequently occur in live poultry markets (LPMs). To gain a better understanding of the evolution of H3 AIVs in China, we conducted country-level AIV surveillance in poultry-associated environments from 2009 to 2022 and conducted large-scale genetic analyses.

Methods

From January 2009 to June 2022, we followed the Chinese Center for Disease Control and Prevention’s AIV surveillance guidelines and gathered environmental samples from avian-related locations across 31 provinces in mainland China on a monthly basis. Out of the 188 H3 viruses we isolated and sequenced, 32 have been previously published [15]. We uploaded the sequence data to the GISAID EpiFlu database (https://www.gisaid.org), with accession numbers EPI2210281-1516, as detailed in Appendix Table 1.

Using the MAFFT version 7.222 software, we aligned the available sequences from the GISAID EpiFlu database as of June 25, 2022. Subsequently, we reconstructed the maximum-likelihood phylogenies of all segments with FastTree version 2.1.11. Based on these trees, we categorized the resulting lineages and sublineages into distinct groups. To determine the genotypes of the full-genome viruses, we assigned combinations of lineages for each segment.

We employed Bayesian Markov chain Monte Carlo analyses in BEAST version 1.10.4 for each gene to determine the time to the most recent common ancestor (tMRCA) of H3N8 viruses in humans. Maximum clade credibility trees were generated and are included in the appendix.

Results

Isolation and Sequencing of H3 AIVs

Avian influenza viruses (AIVs) are a major threat to public health, as they can cause severe respiratory illness in humans and have the potential to cause pandemics. Among AIV subtypes, H3 has shown the potential for cross-species transmission and is a major cause of concern for public health authorities.

In China, H3 AIVs have been circulating dynamically in both wild birds and poultry across multiple regions. To provide a comprehensive picture of the evolution of H3 AIVs in China, researchers conducted country-level AIV surveillance in poultry-associated environments from 2009 to 2022 and performed a large-scale genetic analysis.

Their findings, presented in Figure 1, show the spatial and temporal distribution of H3 subtype viruses isolated from poultry-associated environments in China. The map in Figure 1A indicates that H3 AIVs have been identified in multiple provinces across the country, with H3N2 and H3N8 being the predominant subtypes. One H3 isolate without neuraminidase (NA) was also identified.

The study identified four sublineages of H3 AIVs established in domestic ducks in China via multiple introductions from wild birds from Eurasia. Using full-genome analysis, researchers identified 126 distinct genotypes, with the H3N2 G23 genotype predominating recently.

In April and May 2022, two cases of human infection with AIV subtype H3N8 were reported in China, raising concerns over the potential for a major public health threat. The researchers stressed the importance of ongoing surveillance for H3 AIVs and risk assessment for potential pandemic preparedness.

Overall, the study provides important insights into the evolution and distribution of H3 AIVs in China, highlighting the need for continued vigilance and preparedness in the face of this ongoing public health threat.

Between January 2009 and June 2022, a total of 188 H3 AIVs were isolated from samples collected from poultry-associated environments. Among these, 167 were H3N2, 7 were H3N3, 3 were H3N6, 10 were H3N8, and one had an unknown NA subtype. The H3N2 subtype was found to be widely distributed across 15 provinces in southern China, while the other NA subtypes were isolated in 2 to 8 provinces. The majority of H3 viruses, approximately 79.3% (149/188), were isolated from samples collected from live poultry markets (LPMs). Prior to 2014, the research team had isolated and sequenced a smaller number of H3 AIVs, and the number of isolates increased in the following years, indicating an increase in H3 AIV circulation.

Evolution of H3 Genes in China

The Maximum-likelihood phylogenetic tree shown in Figure 2 represents the hemagglutinin genes of avian influenza viruses subtype H3 isolated from China (n = 1,291) and reference sequences obtained from GISAID (https://www.gisaid.org). The tree sections colored in blue indicate the sequences.

In order to explore the evolution of H3 AIVs in China, we conducted a phylogenetic analysis of the HA genes of the H3 AIVs sequenced in this study and combined them with sequences from the GISAID EpiFlu Database (Figure 2). All viruses in this study were found to belong to the Eurasian lineage, with a nucleotide homology range of 79.2% to 100%. The major branch of the Eurasian avian H3 lineage containing viruses in recent decades was further classified into ten sublineages, which were named according to their geographic distributions, including China-1, China-2, China-3, China-4, Asia, Europe-Asia, worldwide-1, worldwide-2, North America-1, and Korea. In addition, the minor branches at the bottom of the phylogenetic tree included the North America-2 sublineage and early strains sampled during 1972-1992 (Figure 2; Appendix Figure 1). The H3 AIVs collected from wild birds, poultry, or poultry-associated environments in China over the recent decades were found to be distributed in eight sublineages, with the exception of sublineages North America-1, North America-2, and Korea, which were only identified in North America and South Korea.

The AIVs collected from poultry or poultry-associated environments in China, along with a few viruses from Vietnam and Cambodia, were almost exclusively grouped in sublineages China-1, China-2, China-3, and China-4, as shown in Appendix Figure 1. Domestic ducks were identified as the primary host for China-1 (48/166), China-2 (63/111), China-3 (80/110), and China-4 (15/23), as presented in Appendix Table 3. Each sublineage was comprised of various NA subtypes, as seen in Appendix Figure 1, with the most common subtype being H3N2 (270), followed by H3N8 (41), H3N6 (19), H3N3 (12), and H3N9 (1), except for 67 H3 AIVs with unknown NA. These viruses have mainly been sampled since 2009, with recent isolates primarily falling under the China-1 and China-2 sublineages, as illustrated in Figure 2.

In a recent study on the evolution of avian influenza viruses (AIVs) in China, it was found that the China-1 sublineage has evolved into three distinct subgroups, each with different prevalence times. Out of the 185 isolates analyzed, 101 isolates (54.6%) belonged to the China-1.1 subgroup, which has been circulating since 2008 and continues to circulate to this day. Interestingly, three H3N8 strains isolated in 2022 from Fujian and Guangxi provinces were found to have a close relationship with two human H3N8 strains, forming a miniature phylogenetic group. The China-1.2 subgroup was detected during 2009-2016, while the China-1.3 subgroup was detected during 2013-2015. These findings provide valuable insights into the evolution and prevalence of AIVs in China, and highlight the importance of continued surveillance and monitoring of these viruses.

Avian influenza viruses (AIVs) of subtype H3 have been a major concern for public health and poultry industry in China. A recent study conducted by a group of Chinese researchers aimed to investigate the spatial and temporal distribution of H3 AIVs in poultry-associated environments in China from 2009 to 2022. The study revealed that 188 H3 AIVs were isolated from the samples collected from poultry-associated environments during the study period. Among them, 167 were of subtype H3N2, and the rest were of other subtypes, including H3N3, H3N6, H3N8, and one H3 virus with NA unknown.

The H3N2 AIVs were found to be widely distributed across 15 provinces in southern China, whereas other subtypes were identified in 2-8 provinces. More than three-quarters of the H3 viruses were isolated from the samples collected from live poultry markets. A phylogenetic analysis of HA genes of the H3 AIVs sequenced in the study, along with sequences available from the GISAID EpiFlu Database, revealed that the HA genes of all viruses in the study were grouped into the Eurasian lineage and shared a nucleotide homology of 79.2%-100.0%.

The major branch of Eurasian avian H3 lineage containing viruses in recent decades could be further classified into 10 sublineages based on geographic distributions. The sublineages China-1, China-2, China-3, and China-4 consisted of AIVs almost all collected from poultry or poultry-associated environments in China, with domestic ducks acting as the main host. The most common subtype was H3N2, followed by H3N8, H3N6, H3N3, and H3N9. The China-1 sublineage had evolved into 3 distinct subgroups, with prevalence spanning different times.

The China-2 and China-3 sublineages have also evolved into 3 subgroups, with the China-2.2 subgroup mainly comprising environmental H3 viruses sequenced during 2015-2021. On the other hand, H3 viruses of sublineages Asia, Europe-Asia, worldwide-1, and worldwide-2 were occasionally detected in poultry and wild birds in China, but no stable cluster was established.

This study provides important insights into the evolution and distribution of H3 AIVs in China and highlights the need for continued surveillance and control measures to prevent the spread of these viruses and minimize their impact on public health and the poultry industry.

Reassortment with NA Genes

Phylogenetic analyses were conducted on four major NA subtypes, namely N2, N3, N6, and N8, which were detected in each H3 sublineage. The majority of NA genes from H3 AIVs in our study were grouped in the Eurasian lineage, with the exception of eight H3N8 AIVs, whose NA genes originated from the North American lineage (Appendix Figure 2, panels A–D).

Further classification of N2 genes of AIVs in the Eurasian lineage revealed sublineages, and the majority of H3N2 viruses in our study were grouped in the Eurasian-2 sublineage (refer to Appendix). Our investigation also revealed the presence of H3N3 strains that shared a close relationship with the human-origin influenza (H10N3) virus and H3N6 strains that were closely related to the highly pathogenic AIV (HPAIV) subtype H5N6 (refer to Appendix).

Avian influenza virus (AIV) is a highly infectious respiratory disease that affects birds, including chickens, ducks, and turkeys. The virus can be transmitted to humans, and in some cases, it can cause severe illness and even death. The subtype N8 gene is one of the neuraminidase genes found in AIVs, which is essential for the virus’s ability to infect cells.

In Figure 3, a maximum-likelihood phylogenetic tree is shown, which analyzes the subtype N8 genes of AIVs from China (n=1106) and reference sequences from the Global Initiative on Sharing All Influenza Data (GISAID). The blue sections of the tree indicate sequences of H3 AIVs, which are one of the subtypes of avian influenza viruses.

The tree is useful for studying the evolution of AIVs in China and understanding the genetic diversity of the viruses. By analyzing the phylogenetic relationships between the different sequences, researchers can identify the origin of new strains and track the spread of the virus over time. This information is crucial for developing effective vaccines and control measures to prevent the spread of AIVs.

Overall, Figure 3 provides valuable insights into the genetic diversity of AIVs in China and their evolution over time. Further studies will help to better understand the dynamics of the virus and develop more effective strategies for preventing its spread and reducing the risk of human infection.

The majority of H3N8 viruses (43 out of 59) detected in China had NA genes belonging to the North American lineage, which were closely related to AIVs from various regions such as Russia, Vietnam, South Korea, and North America. It is worth noting that the NA genes of human H3N8 and H10N8 viruses were grouped separately, as shown in Figure 3, and three environmental strains sequenced in this study were found to be closely related to human H3N8 viruses. A small number of H3N8 strains identified in China were classified under the Eurasian lineage, as illustrated in Figure 3.

Reassortment with Internal Genes

The phylogenetic tree of each internal gene shows that a significant number of H3 AIVs in China were part of the Eurasian wild bird reservoir (see Appendix Figure 3). Some H3 AIVs had internal genes that originated from different sublineages, such as the ZJ-5 sublineage of wild bird viruses, the poultry H5N1/H5N6 sublineage, the poultry H9N2 ZJ-HJ/07 sublineage, or the waterfowl H6 sublineage (see Appendix). Only one or two virus sequences per internal gene belong to the H9N2 ZJ-HJ/07 sublineage. In 2022, a total of three environmental and two human H3N8 viruses had all internal genes that belonged to the H9N2 ZJ-HJ/07 sublineage.

Emergence of Multiple Genotypes

The H3 subtype of avian influenza viruses (AIVs) has been a major concern in China due to its ability to cause disease in both birds and humans. A recent study has assessed the diversity of genome constellations of H3 AIVs and identified prolific reassortments that have occurred in China in the past decades.

The study analyzed 284 full-genome H3 viruses sampled in China during 2009-2022 and identified 126 genotypes based on the sublineage classification of all 8 gene segments. Among these genotypes, 73 had evidence of dynamic emergence in H3N2 viruses, 11 in H3N3, 17 in H3N6, and 25 in H3N8.

Interestingly, the H3N2 G23 genotype was detected in multiple years and provinces during 2014-2022, indicating its continued circulation. The H3N8 G25 genotype, which was detected in both environmental and human viruses in 2022, had acquired HA genes from the China-1 H3 sublineage, NA genes from the North American N8 lineage, and all 6 internal genes from poultry H9N2 ZJ-HJ/07 sublineage viruses.

The study also found that a large proportion of H3 AIVs in China belonged to the Eurasian wild bird reservoir, with some having internal genes derived from different sublineages such as ZJ-5, poultry H5N1/H5N6, poultry H9N2 ZJ-HJ/07, or waterfowl H6.

The findings of this study highlight the importance of continued surveillance and monitoring of H3 AIVs in China to better understand their diversity and evolution and to inform public health efforts to prevent their spread and potential impact on human health.

Emergence of H3N8 G25 Viruses

Upon analyzing the genetic diversity of G25 genotype viruses, it was found that they shared a higher degree of similarity in their HA (98.4%–99.1%) and NA genes (98.8%–99.3%), but lower similarity in other internal genes such as polymerase basic (PB) 2 (93.9%–100.0%), PB1 (91.6%–99.9%), polymerase acidic (PA) (93.4%–99.6%), nucleocapsid (94.5%–99.9%), matrix (M) (95.3%–100.0%), and nonstructural (97.0%–98.7%). Therefore, this suggests that after the emergence of the prior H3N8 G25 virus, there might have been dynamic reassortment between H3N8 and poultry H9N2 viruses. In order words, the H3N8 G25 virus may have undergone genetic reassortment with poultry H9N2 viruses following its emergence.

The phylogenetic tree in Figure 4 shows the temporal evolution of hemagglutinin (HA) genes from avian influenza virus subtype H3 and neuraminidase (NA) genes from subtype N8 in China, along with reference sequences from GISAID.

A recent study aimed to determine the timing of emergence of the H3N8 G25 virus, which was detected in both human and environmental samples in China in 2022. The researchers performed coalescent analyses and estimated the time of the most recent common ancestor (tMRCA) of all eight virus segments. The results showed that the median tMRCA for the hemagglutinin (HA) gene was estimated to be in February 2021, while the tMRCA for the neuraminidase (NA) gene was estimated to be in August 2020.

The study also identified the closest genetic relatives of the H3N8 G25 virus. The HA genes closely related to the G25 viruses were found in H3N2 AIVs isolated from Guangxi and Guangdong Provinces, particularly in a virus sampled in December 2019. Meanwhile, the NA genes of the G25 viruses were closely related to those of H6N8 AIV isolated in Japan and H3N8 AIV isolated in the Russian Far East during 2019-2020.

This study provides important insights into the emergence and evolution of H3 AIVs in China and highlights the need for continued surveillance and monitoring of influenza viruses in both animals and humans to detect and respond to potential pandemics.

The following statement appears to be incomplete. Could you please provide more context or information so I can properly rephrase it?

In order to better understand the emergence of the H3N8 G25 virus, researchers conducted coalescent analyses to estimate the timing of the most recent common ancestor (tMRCA) for all 8 segments of the virus. The results showed that the tMRCA for the HA genes was estimated to be February 2021, while the tMRCA for the NA genes was estimated to be August 2020. However, the tMRCA for the internal genes of the virus traced back to as early as 2008. It was also noted that the internal genes of the H3N8 G25 viruses did not form a cluster alone, but rather scattered within different subclades. Additionally, the closest H9N2 viruses to the human H3N8 viruses were found to differ, with A/Fujian-siming/1348/2020 (H9N2) being closely related to human H3N8 virus A/Henan/4–10CNIC/2022, and A/Hunan/34179/2018 (H9N2) being close to human H3N8 virus A/Changsha/1000/2022. These findings suggest that the H3N8 G25 viruses underwent dynamic reassortment with H9N2 viruses, and that the internal genes of the virus may have played a significant role in its emergence and evolution.

Molecular Characterization of the H3 AIVs

In our study, we examined the genetic indicators of H3 avian influenza viruses (AIVs) in China, as shown in Appendix Table 5. One human H3N8 isolate, A/Henan/4-10CNIC/2022, had a genetic alteration at position 228, where glycine (G) or serine (S) was replaced, which could modify the virus’s preference for binding to human-type receptors (26). Furthermore, three H3 AIVs collected from poultry in 2014 had an aspartic acid at position 190, which could change the virus’s receptor specificity (26).

The internal gene segments of avian H3 viruses in China have been found to possess key molecular markers that are associated with increased capacity for receptor binding, viral replication, and pathogenicity in mammals, according to Appendix Table 5. The presence of E627K and E627V mutations in PB2 genes exclusively in human H3N8 viruses suggests that these viruses have adapted to mammals. Other mutations such as R389K, I292V, and A588V in PB2, which are believed to be associated with increased polymerase activity and replication in mammalian and avian cells, as well as virulence in mice, were also found in 2 human isolates and several avian H3 viruses. All H3 AIVs were found to contain N30D, T215A, and P41A mutations in the M1 genes, which could alter the virulence in mice and affect growth and transmission in the guinea pig model. The identification of these molecular markers could aid in the early detection and control of potentially pathogenic H3 viruses in both avian and mammalian populations.

Host-specific amino acids were identified in the PB2 and PA genes of human H3N8 isolates and some H3 AIVs (PB2-702R, PA-356R, PA-409N), with the exception of A/Changsha/1000/2022, which had PB2-702K. The substitutions related to antiviral drug resistance were also analyzed, and two human H3N8 viruses contained an S31N mutation in the M2 gene, indicating resistance to amantadine and rimantadine. Mutations such as E119V/A/D and H274Y (N2 numbering) were not identified in the NA gene, indicating that all H3 viruses might be sensitive to NA inhibitors (e.g., oseltamivir). However, three H3 AIVs possessed Q136L, E119G, or H274R, which could potentially affect their drug sensitivity. In the M2 protein, 26 out of 337 H3 AIVs contained the drug-resistance mutation V27I/A, and 15 contained S31N. These findings are presented in Appendix Table 5 and Figure 14.

Discussion

AIVs are naturally present in waterfowl and spread globally through wild bird migration. They are introduced to domestic poultry through contact with wild birds, leading to continuous circulation of H3 AIVs in poultry and wild birds in China. Over the past few decades, four sublineages of the Eurasian lineage have emerged in China, including China-1, China-2, China-3, and China-4, which have predominantly circulated in domestic ducks. Currently, China-1 and China-2 sublineages are co-circulating in poultry, with China-1 being more common. While other sublineages such as Worldwide-1 have been introduced into poultry from wild birds, continuous introductions may lead to the emergence of new sublineages in poultry. From 2009 to 2022, H3N2 was the most prevalent subtype of H3 AIVs in poultry-associated environments. The available avian strains in GISAID corroborate these findings, although most were collected during 2013–2015 due to the increased surveillance during the H7N9 influenza outbreak.

The molecular analyses conducted indicated that H3 AIVs had undergone extensive reassortment, resulting in the emergence of numerous genotypes. We were able to identify a total of 126 genotypes from the 284 H3 AIVs that were analyzed during the period of 2009-2022, with the majority of these genotypes being transient. The H3N2 G23 genotype appears to have stabilized in recent years, and it is currently the predominant genotype in southern China. The H3N8 G25 viruses, which were responsible for human infections, had a complete internal gene cassette that was derived from the H9N2 ZJ-HJ/07 sublineage of poultry. This H9N2 AIV sublineage has been circulating persistently in chickens in China and is referred to as the G57 genotype. Similar to the H7N9 AIVs, it is likely that the H3N8 G25 AIVs have adapted to chickens rather than ducks.

The H3N8 G25 viruses displayed different tMRCAs for each of their 8 segments. Based on the molecular dating of the HA and NA genes, it was suggested that the ancestral virus of H3N8 G25 might have been created by the reassortment of the H3N2 G23 virus and a wild bird H3N8 virus, prior to February 2021 (95% HPD: October 2020 – May 2021). However, the internal genes of the H3N8 G25 viruses showed an earlier tMRCAs than those of the HA and NA genes, indicating that the emergence of H3N8 G25 viruses might be due to sequential reassortments.

For a considerable period, H3 AIVs had been in existence, yet no instance of human infection was reported until 2022. After reassortment with six internal genes of H9N2, current H3N8 AIVs appear to possess the advantage of infecting humans (42). The emergence of pandemic strains might be due to ongoing adaptation in mammals after continuous human infections. The H3N8 G25 viruses that caused human infections had acquired human-adapted mutations (such as 228G/S in the HA gene and E627K/V in the PB2 gene) after infecting humans (Appendix Figure 14), and these mutations were also present in 1968 H3N2 pandemic strains (43). This finding suggests the pandemic potential of the newly emerged H3N8 AIVs.

In the wake of the emergence of the H3N8 G25 avian influenza virus, understanding the potential pandemic risk is crucial. One critical parameter in assessing this risk is the level of human population immunity to the newly emerged virus. According to recent studies, there is little or no preexisting immunity to the H3N8 virus in the human population. In particular, seropositivity for the human seasonal H3N2 virus did not correlate with immunity to the H3N8 virus.

Given this lack of preexisting immunity, it is essential to prepare for a potential pandemic by stockpiling vaccines and drugs that could be effective against the H3N8 virus. Additionally, since no drug-resistance mutation to NA inhibitors was observed in the H3N8 G25 viruses, these inhibitors may be effective in treating or preventing infection.

It is also important to continue monitoring the evolution of the H3N8 virus and its potential for human-to-human transmission. Ongoing adaptation in mammals after continuous human infections could increase the risk of pandemic strains emerging in the future. Therefore, increased surveillance, research, and preparation are needed to mitigate the potential impact of the H3N8 virus on human health.

Avian influenza viruses (AIVs) are a group of viruses that primarily infect birds but can also cause illness in humans and other animals. The H3 subtype of AIVs has been circulating in poultry and wild birds in China for many years, and recently a new strain of H3N8 AIVs emerged that is of concern due to its potential to cause a pandemic.

One critical factor in assessing the risk of a pandemic is the level of population immunity to the virus. Recent studies have shown that the human population has little or no preexisting immunity to the newly emerged H3N8 AIVs, indicating the need for vaccine and drug stockpiles for potential pandemic preparation.

While H3 AIVs have been isolated from asymptomatic ducks, recent research has shown that the newly emerged H3N8 AIVs are pathogenic to chickens. Samples collected for surveillance in this study were exclusively from avian-linked environments, including live poultry markets, poultry farms, backyards, and slaughterhouses, but the data collected might be biased due to the limited number of sites sampled.

More information is needed about the species of poultry in these locations to understand the spatiotemporal differences in H3 AIV activity. It is essential to continue monitoring AIVs in poultry and wild birds to better understand their spread and evolution and to help prevent and prepare for potential pandemics.

The surveillance of AIVs has improved significantly since the HPAIV H5N1 infected humans in Hong Kong in 1997 (47). However, despite these efforts, gaps in the surveillance still exist, and the emergence of new viruses remains unpredictable. The AIVs circulating and evolving in poultry may have a preference for direct transmission to humans, particularly at the poultry-human interface (48). The H3N8 G25 viruses have raised concerns about their pandemic potential, as they have increased human receptor binding and low population immunity (12). Additionally, many H3 AIVs have dual receptor-binding profiles (49,50), as well as mutations that enhance virus replication and pathogenicity in mammals. As a result, surveillance and research on H3 AIVs, as well as the capacity for drugs and vaccines, should be strengthened to prepare for pandemics.

Dr. J. Yang is a researcher who works at several institutions, including the Chinese National Influenza Center, the National Institute for Viral Disease Control and Prevention, the Chinese Center for Disease Control and Prevention, and the School of Public Health (Shenzhen), which is located on the Shenzhen campus of Sun Yat-sen University. Her research focuses on the epidemiology and evolutionary analysis of influenza viruses.

Acknowledgments

The sharing of scientific data is an essential aspect of research collaboration and advancement. In the case of the study of avian influenza viruses, the authors and laboratories who contributed to the GISAID database deserve thanks for their efforts. The availability of genomic sequences of AIVs has allowed for a better understanding of their evolution and transmission, which is vital in developing effective strategies for control and prevention.

By making their data publicly accessible, these researchers have enabled the scientific community to collaborate and analyze the virus’s genetic diversity on a global scale. This data-sharing practice promotes transparency and encourages cooperation among scientists to develop timely and effective interventions for emerging diseases. Furthermore, it enables researchers to build on each other’s work, leading to more significant breakthroughs and innovations in the field of virology.

The importance of data sharing cannot be overstated, especially during a pandemic. The AIV surveillance data generated from this study is a valuable resource that can be used to inform public health policies and strategies, including the development of vaccines and antivirals. It is important to recognize the contributions of all those who have made this data available and to continue to encourage open science practices in the future.

Funding for this study was provided by the National Key Research and Development Program of China (2022YFC2303800, 2021YFC2300100) and the National Natural Science Foundation of China (81961128002, 31970643).

The viewpoints expressed by the authors who contribute to this journal may not necessarily mirror the perspectives of the institutions with which they are associated or the Chinese Center for Disease Control and Prevention.

References

Pu J, Zhang GZ, Ma JH, Xia YJ, Liu QF, Jiang ZL, et al. Detection of avian H3 subtype influenza virus antibodies in chickens by serological tests. Avian Dis. 2009;53:198-204. doi: 10.1637/8362-081508-Reg.1. PubMed PMID: 19432034.

Hollander LP and colleagues’ research report titled “Prevalence of Influenza A Viruses in Ducks Sampled in Northwestern Minnesota and Evidence for Predominance of H3N8 and H4N6 Subtypes in Mallards, 2007-2016” was published in Avian Diseases in 2019.

The study conducted by Kang HM et al. aimed to investigate the genetic characteristics of avian influenza viruses in Mongolia between 2007 and 2009 and their relationship with Korean isolates from domestic poultry and wild birds. The researchers collected a total of 106 avian influenza virus samples from domestic poultry and wild birds in Mongolia and analyzed their genetic sequences. They found that the majority of the avian influenza viruses isolated in Mongolia belonged to the H5 and H9 subtypes, with a small number of H7 and H6 subtypes.

The genetic analysis showed that the H5N1 viruses in Mongolia were closely related to those found in Korea, indicating that there may be continuous transmission of avian influenza viruses between the two countries. The study also revealed that some of the avian influenza viruses in Mongolia had unique genetic characteristics that were not found in other countries, suggesting that Mongolia may be an important reservoir for avian influenza viruses.

Overall, the study highlights the importance of continued surveillance and genetic analysis of avian influenza viruses in order to better understand their evolution and transmission patterns. It also underscores the need for international collaboration and coordination in the prevention and control of avian influenza, particularly in areas where the virus is endemic.

The avian influenza viruses belonging to the H3 subtype isolated from poultry in Vietnam were characterized in this study by Soda et al. (2020). The researchers analyzed the genetic makeup of these viruses and compared them with other H3 subtype viruses. Their findings suggested that the H3 subtype viruses in Vietnam showed genetic diversity and were closely related to the H3 viruses circulating in China and other Asian countries. The study also highlighted the importance of continued surveillance and monitoring of avian influenza viruses in poultry to identify potential threats to human health.

The following is a possible rephrased version of the text:

Avian influenza viruses of the H3 subtype have been isolated from both domestic ducks and wild birds in Korea, and their genetic relationship has been investigated. The pathogenic potential of these viruses in chickens and ducks has also been evaluated. This study was conducted by Choi JG and colleagues, and the results were published in the journal Veterinary Microbiology in 2012.

In 2011, a group of harbor seals were found dead on the coast of New England. Scientists discovered that the seals had been infected with a strain of avian influenza virus known as H3N8. This was the first time that this particular virus had been detected in seals, and it was also the first time that any type of avian influenza virus had been identified as the cause of a marine mammal die-off.

The H3N8 virus is a type of influenza A virus that normally infects birds, particularly waterfowl such as ducks and geese. It is not uncommon for influenza viruses to jump between species, and it is thought that the seals became infected with the virus after coming into contact with infected birds.

The discovery of H3N8 in seals raised concerns about the potential for the virus to spread to other marine mammals and even to humans. While there have been no reported cases of H3N8 infection in humans, scientists continue to monitor the virus closely.

This study was a reminder of the importance of monitoring animal populations for signs of disease outbreaks, as well as the need for continued research into the ways in which viruses can jump between species. By understanding how viruses are transmitted and how they evolve, scientists can develop strategies to prevent and control the spread of disease in both animal and human populations.

The following is a possible rephrased version of the text:

In 1992, a novel influenza A virus with avian-like characteristics was discovered in horses in China. The virus was characterized by Guo et al. and found to be genetically distinct from previously identified equine influenza viruses. The study, published in Virology, reported on the virus’s molecular features and antigenicity and provided insights into its possible origin and transmission.

Equine H3N8 influenza viruses have been isolated and their molecular characterization was studied by Tu J and colleagues. The study was conducted in China where the equine influenza virus was isolated from pigs. The researchers analyzed the genetic makeup of the virus and found that it was closely related to the equine influenza viruses that are circulating in horses. The study provides important insights into the transmission of influenza viruses between different animal species and highlights the need for continued surveillance to monitor the emergence of new influenza strains. The study was published in the journal “Archives of Virology”.

The following text has been paraphrased:

The text suggests that equine influenza virus has the ability to infect dogs and spread between the two species. The study, conducted by Crawford and his colleagues, showed that the infected dogs were not only able to transmit the virus to other dogs but also to humans. This was the first report of equine influenza virus being transmitted to humans. The researchers concluded that the virus had adapted to infect a new host and was now capable of causing disease in both horses and dogs.

The emergence of pandemic influenza viruses is discussed in an article by Guan Y et al. published in Protein Cell in 2010. The article focuses on the factors that contribute to the emergence of pandemic influenza viruses, including genetic reassortment, antigenic drift and shift, and host range adaptation. The authors also discuss the epidemiology and evolution of pandemic influenza viruses, as well as the challenges associated with surveillance, diagnosis, and control of these viruses. Overall, the article provides a comprehensive overview of the emergence of pandemic influenza viruses and their potential impact on public health.

The following is a possible rephrased version of the text:

An epidemiological investigation study conducted by Bao and colleagues reported a case of human infection with a reassortment avian influenza A H3N8 virus. The study, published in Nature Communications in 2022, details the investigation of the case and describes the genetic analysis of the virus. The findings suggest that the virus resulted from the reassortment of avian influenza viruses and underscores the ongoing risk of zoonotic transmission of influenza viruses from animals to humans.

A recent study published in The Lancet Microbe describes a case of human infection with avian influenza A H3N8 virus. The report provides insights into the transmission and genetic origins of the virus.

The patient in question was a 71-year-old woman from Jiangsu province in China, who developed flu-like symptoms in November 2021. She was admitted to the hospital and diagnosed with pneumonia. Laboratory tests revealed that she was infected with avian influenza A H3N8 virus.

The authors of the study conducted a thorough investigation of the patient’s exposure to birds and poultry markets, as well as genetic analyses of the virus. The results showed that the virus was a reassortment of avian influenza viruses from wild birds and domestic poultry.

The study provides evidence of the zoonotic potential of avian influenza viruses and highlights the importance of continued surveillance of these viruses in both animals and humans. The authors emphasize the need for increased monitoring of poultry markets and strict control measures to prevent the spread of avian influenza viruses.

The emergence of novel influenza viruses with pandemic potential is a serious threat to global public health. This study serves as a reminder of the need for ongoing surveillance and research to understand the transmission and genetic characteristics of these viruses, in order to prevent and control future outbreaks.

Influenza A(H3N8) is a subtype of the influenza virus that primarily infects birds but has also been known to infect horses, dogs, and seals. Recently, there have been concerns about its potential to cause a major public health threat if it were to jump from animals to humans. In a study published in the International Journal of Infectious Diseases, researchers Yassine HM and Smatti MK examined the characteristics of the H3N8 virus and the potential risks it poses to human health.

According to the researchers, several factors make H3N8 a potential threat to human health. Firstly, it is a highly pathogenic virus that can cause severe illness and death in animals, and therefore may have similar effects in humans if it were to infect them. Secondly, H3N8 has shown the ability to reassort with other influenza strains, potentially leading to the emergence of new and more dangerous strains. Finally, H3N8 has been found to be capable of infecting human cells in laboratory experiments, indicating that it has the potential to jump from animals to humans.

While the risk of H3N8 causing a major public health threat is currently low, the researchers caution that continued surveillance is necessary to monitor for any changes in the virus that could increase its potential to infect humans. They also emphasize the importance of preparedness efforts to ensure that the world is ready to respond quickly and effectively to any potential outbreaks of H3N8 or other emerging infectious diseases.

The H3 subtype avian influenza virus (AIV) has been a persistent threat to both poultry and human health in China. In a recent study published in China CDC Weekly, researchers investigated the epidemiological and genetic characteristics of H3 subtype AIVs circulating in China from 2015 to 2019.

The study analyzed a total of 524 H3 subtype AIV isolates collected from domestic poultry and wild birds in 21 provinces across China. The results showed that the prevalence of H3 subtype AIVs in China exhibited a seasonal pattern, with higher incidence rates in the winter and spring months. Notably, the H3N2 and H3N8 subtypes were found to be the dominant subtypes circulating in China during the study period.

Genetic analysis revealed that the H3 subtype AIVs isolated from domestic poultry and wild birds in China shared a high degree of genetic similarity with each other, suggesting a potential for interspecies transmission. The researchers also identified several genetic changes in the H3 subtype AIVs that may contribute to their pathogenicity and ability to adapt to new hosts.

Overall, the study highlights the importance of continued surveillance and monitoring of H3 subtype AIVs in China and underscores the need for effective measures to prevent and control AIV transmission.

Here’s a possible rephrased text:

Between 2014 and 2017, avian influenza viruses of the H3 subtype were identified in samples collected from poultry-related environments in China. Zou and colleagues conducted molecular analyses of these viruses and reported their findings in a study published in Virology. Their study characterized the genetic makeup of the H3 subtype viruses and provided insights into their prevalence and diversity in different regions of China during the surveillance period.

Here’s a rephrased version of the text:

In 2016, a study was conducted to investigate the pathogenicity of H3 subtype avian influenza viruses isolated from live poultry markets in China, through phylogenetic analysis. The researchers analyzed the genetic relationship between these viruses and other H3 subtype viruses, as well as their pathogenic potential. The study was published in the journal Scientific Reports.

Avian influenza, also known as bird flu, is a highly infectious viral disease that affects birds and occasionally infects humans. The Greater Mekong Subregion, which includes countries like Cambodia, Laos, Myanmar, Thailand, and Vietnam, is a region where avian influenza has been endemic for many years.

A study published in 2019 by Suttie and colleagues investigated the incidence and diversity of avian influenza viruses in the Greater Mekong Subregion from 2003 to 2018. The study found that the H5 and H9 subtypes were the most prevalent in the region, with sporadic outbreaks of H7, H6, and H10 subtypes.

The study also highlighted the importance of wild birds in the spread of avian influenza, as many of the viruses isolated from poultry were similar to those found in wild birds. The authors suggested that continued surveillance of wild birds and poultry in the region was necessary to monitor the emergence of new avian influenza viruses and prevent their spread to humans.

The study also emphasized the need for improved vaccination programs and biosecurity measures in the poultry industry to reduce the risk of avian influenza outbreaks and limit their impact on both animal and human health.

Overall, the study highlights the ongoing threat of avian influenza in the Greater Mekong Subregion and the importance of continued surveillance and prevention efforts to control the disease.

Rewritten: The low pathogenic avian influenza viruses of H3 subtype, isolated from wild mallards in Poland, were subject to phylogenetic studies by Olszewska et al. in Acta Vet Hung, 2013.

Rewritten:

In a local community in Hunan Province, China, there was co-circulation of H5N6, H3N2, and H3N8, along with the emergence of a novel reassortant H3N6 virus, according to a study by Li X et al. published in Scientific Reports in 2016. The researchers analyzed the genetic characteristics of these avian influenza viruses and identified their potential to infect humans. The co-circulation of different subtypes of avian influenza viruses in the same location is concerning, as it increases the likelihood of reassortment events and the emergence of new potentially pathogenic strains.

The H3N2 avian influenza viruses that were isolated from live poultry markets and poultry slaughterhouses in Shanghai, China in 2013 were genetically analyzed by Yang et al.

The following text has been rephrased:

A novel influenza virus of the H3N2 subtype was discovered in domestic ducks in China, and its characteristics were examined. Li and colleagues conducted the study, which was published in Virus Genes in 2016.

Here’s a possible rephrased version:

In a poultry market located in south central China, researchers found a diverse range of influenza virus genes. Liu and colleagues conducted a study where they analyzed samples collected from the market in 2001 and identified multiple influenza A virus subtypes, including H3N2, H5N1, and H9N2. The presence of multiple influenza subtypes in a single location highlights the potential for viral reassortment and the emergence of novel strains with pandemic potential. The study underscores the importance of continued surveillance and monitoring of influenza viruses in animal populations to mitigate the risk of zoonotic transmission to humans.

The performance and usability of the MAFFT multiple sequence alignment software version 7 have been improved, according to Katoh K and Standley DM. In their article published in Molecular Biology and Evolution in 2013, they discussed the enhancements made to the software.

The following is a possible rephrased version of the text:

FastTree 2 is a software tool that constructs nearly maximum-likelihood phylogenetic trees for large sequence alignments in a short time. The algorithm used in FastTree 2 is based on the neighbor-joining method and optimized through a refinement step using maximum-likelihood criteria. Price et al. developed and validated the tool, which is widely used in bioinformatics and computational biology.

The following is a possible rephrased version:

BEAST 1.10 is a tool for integrating Bayesian phylogenetic and phylodynamic data, developed by Suchard MA, Lemey P, Baele G, Ayres DL, Drummond AJ, and Rambaut A. This software enables the estimation of evolutionary rates and timescales of different lineages, while also allowing for the incorporation of prior knowledge on the biology of the organisms under study. The use of BEAST 1.10 can help researchers understand the evolutionary relationships among different strains of viruses, such as influenza, and infer the patterns and drivers of their spread and diversification.

One possible rephrased text is: In a recent study, Thompson and Paulson investigated the process of adaptation of influenza viruses to human airway receptors. The research, which was published in the Journal of Biological Chemistry, provides insights into the molecular mechanisms underlying the ability of influenza viruses to infect humans. The study highlights the importance of understanding the interactions between viral surface proteins and host cell receptors for the development of effective strategies to prevent and control influenza infections. The findings of this study may have important implications for the design of novel therapeutics and vaccines against influenza viruses.

The H7N9 strain of influenza A virus has caused several outbreaks in humans since its first appearance in China in 2013. This virus can cause severe respiratory illness and has a high mortality rate. A study published in 2017 in the journal Virology identified two specific mutations in the PB2 gene of the H7N9 virus that increased its virulence in mammals.

The study found that the mutations, called V598T and V598I, resulted in increased replication of the virus in mammalian cells and enhanced pathogenicity in mice. The researchers also observed that these mutations altered the binding affinity of the PB2 protein to host cell factors, allowing the virus to better adapt to and infect mammalian hosts.

These findings have important implications for public health, as they suggest that surveillance of H7N9 viruses should include monitoring for these specific mutations in the PB2 gene. This information can aid in the development of more effective vaccines and antiviral therapies against this highly pathogenic virus. Additionally, it underscores the importance of continued vigilance in monitoring and responding to emerging infectious diseases, particularly those with pandemic potential.

The dominant I292V mutation in PB2 of avian influenza H9N2 virus enhances viral polymerase activity and weakens the induction of IFN-β in human cells, according to a study published in the Journal of General Virology in 2019 by Gao et al.

Avian influenza viruses, also known as bird flu viruses, are typically found in birds and do not usually infect humans. However, some strains of avian influenza viruses have been known to cause severe illness and death in humans. Scientists have been studying these viruses in order to better understand how they adapt and spread to humans.

One study conducted by Xiao et al. and published in Scientific Reports in 2016 found that a specific mutation in the PB2 gene, called PB2-588V, played a crucial role in the mammalian adaptation of several avian influenza viruses, including H10N8, H7N9, and H9N2. This mutation enhanced the ability of these viruses to infect mammalian cells and replicate in mammalian hosts.

The researchers used reverse genetics to generate avian influenza viruses with different PB2 genes and tested their virulence in mice. They found that the H10N8 virus with PB2-588V was able to infect mice without prior adaptation, causing severe disease and death. In contrast, the virus with the wild-type PB2 gene did not cause any symptoms in the mice.

The study also showed that the PB2-588V mutation increased the expression of viral polymerase complex and enhanced viral replication in mammalian cells. In addition, the PB2-588V mutation attenuated the induction of interferon-beta (IFN-β), which is an important antiviral cytokine produced by the host’s immune system in response to viral infections.

Overall, these findings suggest that the PB2-588V mutation plays a critical role in the adaptation and pathogenicity of avian influenza viruses in mammals. Further research is needed to better understand the molecular mechanisms underlying this adaptation and to develop strategies to prevent or treat these viruses.

Influenza viruses, including the highly pathogenic H5N1 avian influenza virus, have been a significant public health concern. Understanding the genetic determinants of virulence can provide insights into the development of effective treatments and vaccines.

A study published in Virology in 2009 by Fan et al. investigated the role of two amino acid residues in the matrix protein M1 of H5N1 avian influenza viruses in mice. The researchers found that these two residues contributed to the virulence difference between H5N1 viruses isolated from different avian species.

The study used reverse genetics to generate recombinant H5N1 viruses with mutations at the two amino acid positions of interest. The recombinant viruses were then tested in mice for virulence and pathogenicity.

The results showed that mutations at the two amino acid positions led to a significant decrease in virulence in mice, indicating that these residues play an important role in determining the pathogenicity of the virus.

This study highlights the importance of understanding the genetic determinants of virulence in influenza viruses. Identifying these key residues can help to develop effective treatments and vaccines, as well as inform surveillance and control efforts for emerging influenza viruses.

Influenza A viruses are known to cause respiratory illnesses in humans, birds, and swine. The transmission of these viruses is a complex process that involves various viral proteins. One of these proteins is the matrix protein M1, which plays a critical role in the assembly and release of virus particles.

Researchers have been studying the role of M1 in the virulence of different influenza A viruses. In a study published in the Journal of Virology in 2014, Campbell et al. investigated the impact of a specific residue, residue 41, of the M1 protein on the virulence and transmission of Eurasian avian-like swine influenza A virus.

The researchers used reverse genetics to create a mutant virus that had a change in the M1 residue 41. They found that this mutant virus had shorter virion filaments than the wild-type virus, indicating that residue 41 plays a role in determining virion length.

Furthermore, the mutant virus showed reduced transmission efficiency in a direct-contact transmission model, indicating that residue 41 also plays a role in determining transmission efficiency.

These findings suggest that residue 41 of the M1 protein may be a potential target for developing strategies to control the transmission of influenza A viruses. The study highlights the importance of understanding the molecular mechanisms that govern the virulence and transmission of influenza viruses in order to develop effective control strategies.

The following is a possible rephrased version of the text:

In Microbes and Infection, Liu et al. (2013) presented their analysis of a new strain of influenza A (H7N9) virus that emerged in China and caused an outbreak in humans. Their study utilized both genomic signature and protein sequence analysis to identify the characteristics of this novel virus.

The following is a possible rephrased version of the text:

In Microbes and Infection, Liu et al. (2013) presented their analysis of a new strain of influenza A (H7N9) virus that emerged in China and caused an outbreak in humans. Their study utilized both genomic signature and protein sequence analysis to identify the characteristics of this novel virus.