Navigating the H5N1 avian influenza threat in Vietnam and global public health implications

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Dear Editor, Influenza A viruses, particularly the H5N1 subtype, have been a focal point of global health concerns because of their pandemic potential and high mortality rates in humans. The avian influenza A (H5N1) virus, first identified in humans in 1997, causes sporadic infections. Avian influenza, a zoonotic disease, predominantly has bird-to-human transmission through direct or indirect contact with infected animals or feces contaminated with surfaces/environments1–3. Figure 1 illustrates the complex transmission cycle of H5N1 virus, encompassing both natural and zoonotic pathways, highlighting the critical points of viral transmission among various hosts. The virus travels from natural carriers, such as shorebirds and waterfowl, to intermediate hosts, including poultry and mammals. Poultry, serving as a primary vector, play a pivotal role in bridging the gap between wild bird reservoirs and human infections. The virus can mutate, with mutated strains posing different levels of threat to birds and mammals, including humans. Notably, human activities such as farming and hunting can facilitate zoonotic transmission, demonstrating the capacity of the virus to jump from animals to humans through direct or indirect contact with infected animals or contaminated environments. The global spread of H5N1 since 2003, with 888 human cases reported to WHO from 23 countries with a case fatality rate of 52% illustrates the complex challenge of controlling zoonotic influenza3. The persistence of H5N1 in poultry populations, particularly in rural and agricultural settings, poses a continuous risk of human infections4.Figure 1: Transmission cycle of the H5N1 Avian influenza virus.Despite the low transmission rates among humans, the virus’s high mortality rate and potential for mutation make it a significant public health threat. The recent notification by Vietnam to the WHO of a human case of H5N1 avian influenza—the first since 2022—serves as a stark reminder of the virus’s persistence in the environment and its capacity to cross species barriers1. Infected humans can present with mild upper respiratory tract infection, severe pneumonia, sepsis, acute respiratory distress syndrome, and shock, which can lead to death. A recent case in Vietnam involved a young male from Khanh Hoa Province who initially had fever and cough for 4 days since 11 March 2024, before being admitted to the hospital on 15 March 2024, with persistent symptoms, including abdominal pain and diarrhea. Detailed investigation revealed a history of bird hunting in February 20241. On 19 March 2024, a real-time polymerase chain reaction (RT-PCR) test was positive for H5 influenza virus. In addition, genomic sequencing performed on 22 March 2024, reported H5N1 virus presence. Over the following week, he developed severe pneumonia, severe sepsis, and acute respiratory distress syndrome, ultimately leading to death on 23 March 2024. This case illustrates the ongoing risk of zoonotic spillover, and the critical need for vigilant surveillance and response mechanisms. Following the confirmation of the H5N1 infection, the Vietnamese government, in coordination with the WHO, initiated a comprehensive response, including epidemiological investigations, disinfection of the patient’s residence and suspected exposure sites, and close monitoring and testing of contacts and local poultry1. These actions, aligned with international health regulations, emphasize the importance of rapid response, and containment measures in managing zoonotic outbreaks. This recent case in Vietnam not only highlights the need for ongoing vigilance but also raises questions regarding the effectiveness of current surveillance and response strategies in the face of evolving viral threats. As detailed in Table 1, strategies for mitigating avian influenza include strengthening surveillance systems to swiftly detect and respond to outbreaks, enhancing public health infrastructure to support effective treatment and containment, and fostering global collaboration for shared knowledge and resources. Additionally, community engagement is critical for educating the public on preventive measures, while ongoing research on vaccines and antivirals ensures preparedness for future outbreaks. Table 1 - Strategies for mitigating avian influenza outbreaks. Strategies Description Strengthening surveillance systems Enhanced surveillance of avian populations and early warning systems for zoonotic spillover. Investment in technologies and methodologies for rapid detection and characterization of novel influenza strains Enhancing public health infrastructure Strengthening health infrastructure, especially in rural and agricultural areas prone to zoonotic transmission. Improving access to healthcare, enhancing laboratory capabilities, and ensuring availability of antiviral medications Global collaboration and information sharing Facilitating global cooperation by sharing epidemiological data, research findings, and best practices among countries and international organizations. Coordinated response to influenza outbreaks Community engagement and education Conducting public awareness campaigns to highlight risks associated with direct contact with birds and importance of hygiene practices. Engaging communities in surveillance efforts for early detection and response Vaccine development and antiviral research Continued investment in vaccine development against zoonotic influenza strains and research into effective antiviral treatments. Support for WHO’s efforts to update candidate vaccine viruses for pandemic preparedness The recent H5N1 outbreak in Vietnam exemplifies significant advancements in the country’s disease surveillance and response systems compared to past episodes, notably the 1997 Hong Kong outbreak and the 2004 outbreak in Vietnam. During the 1997 outbreak, delays in recognizing the virus and implementing containment measures led to widespread transmission and significant mortalities5. In contrast, the rapid identification and response in 2024 cases, including immediate RT-PCR testing and coordinated efforts with the WHO, highlight improvements in real-time surveillance and genetic sequencing capabilities. These advancements have enabled more precise and quicker interventions with the potential to save lives. Furthermore, the integration of digital epidemiology tools has played a crucial role in tracking the spread and mutation of the virus, demonstrating a marked progression from the manual tracking methods used in earlier outbreaks6,7. Overall, the recent H5N1 case in Vietnam is a critical reminder of the ongoing threat posed by the zoonotic influenza viruses to global health. Although the risk to the general population remains low, the potential for these viruses to mutate and spread among humans necessitates vigilant surveillance, rapid response, and global cooperation. By strengthening public health infrastructure, enhancing surveillance systems, and investing in research and development, the international community can better prepare for and mitigate the impact of future zoonotic outbreaks. Ethical approval The information provided in the manuscript does not require an ethics application or approval. Consent No patients were sorted. Not applicable. Sources of funding Not applicable. Author contribution A.A.: conceptualization, supervision, writing – original draft, and writing – review and editing; A.V., M.N.K., Q.S.Z., A.M.G., N.K., S.R., and P.S.: writing – original draft and writing – review and editing. Conflicts of interest disclosure The authors declare no conflicts of interest. Research registration unique identifying number (UIN) Not applicable. Guarantor Ayush Anand. Data availability statement Data sharing is not applicable to this article. Provenance and peer review Not commissioned, externally peer-reviewed.