Draft:Avian Influenza

Avian Influenza a one health issue

Avian influenza, commonly known as bird flu, is a contagious viral infection primarily affecting bird species caused by Type A influenza viruses. The disease occurs naturally among wild aquatic birds but also spreads to domestic poultry and, in rare instances, humans and other animals. Notable strains that have crossed the species barrier include H5N1, H7N9, and H5N6[^1][^2].

Background

Avian influenza viruses circulate globally among natural reservoirs such as wild birds; these viruses often cause little or no harm in wild bird populations but can mutate and become highly pathogenic when transmitted to domestic poultry, resulting in severe outbreaks[^3][^4]. The viruses are classified based on pathogenicity:

  - Low pathogenic avian influenza (LPAI): Typically causes mild symptoms in birds but has the potential to evolve into highly pathogenic strains[^5].
  - Highly pathogenic avian influenza (HPAI) Causes severe disease and high mortality in birds and can infect humans, leading to critical health outcomes[^6].

Epidemiology Avian influenza has been reported worldwide, with significant outbreaks in Asia, Africa, and Europe due to dense poultry farming practices and migratory bird pathways[^7]. The H5N1 strain was first identified in 1996 in Guangdong, China, and it eventually spread to multiple countries, causing human infections in addition to affecting poultry[^8].In 2023, the World Health Organization (WHO) documented over 860 confirmed human cases of H5N1, with a case fatality rate of approximately 53%[^9].The H7N9 strain, reported in China in 2013, has also caused a series of human infections. Epidemiological studies indicate that most human infections arise from exposure to live bird markets or handling infected poultry[^10]. Outbreaks are most often found in areas where people and birds are in close proximity, such as live bird markets, facilitating zoonotic transmission[^11].

Transmission Avian influenza spreads primarily among birds through direct contact with infected birds’ saliva, nasal secretions, and feces. Wild birds introduce the virus into new regions via migration, infecting domestic birds[^12].

Humans become infected primarily through:

  - Direct contact Handling, slaughtering, or preparing infected poultry without protective measures[^13].
  - Environmental exposure: Visiting live bird markets or environments contaminated with the virus[^14].
  - Consumption: less commonly Eating undercooked poultry products may pose a risk [^15].

Human-to-human transmission remains rare and is usually limited to close family members or healthcare workers in contact with infected individuals[^16].

Symptoms in Humans Human infections with avian influenza viruses can lead to a range of symptoms, from mild respiratory issues to severe and fatal complications. Common symptoms include fever, cough, sore throat, and muscle aches, while severe cases may progress to pneumonia, acute respiratory distress syndrome (ARDS), and multi-organ failure[^17]. The H5N1 strain has shown a high mortality rate among infected individuals, with approximately 53% of confirmed cases resulting in death[^18]. This high fatality rate shows the need for rapid medical intervention and early antiviral treatment[^19].

Prevention and Control 1. Surveillance and Monitoring: National and international bodies, including the WHO Food and Agriculture Organization (FAO) and the World Organisation for Animal Health (OIE), monitor avian influenza outbreaks globally[^20][^21].

2. Biosecurity Measures: Poultry farms implement strict biosecurity protocols to reduce the risk of virus introduction, such as isolating domestic poultry from wild birds and disinfecting equipment and facilities[^22].

3. Culling and Vaccination: Infected flocks are often culled to contain outbreaks, and vaccines are administered to poultry in some regions to protect against common strains, although effectiveness varies due to the virus's rapid mutation[^23].

4. Public Health Campaigns Public awareness initiatives educate people on the safe handling of poultry and discourage visiting live bird markets during outbreaks to reduce human infections[^24].

Treatment Human cases of avian influenza are treated with antiviral medications like oseltamivir and zanamivir, which can reduce symptom severity [^25]. Supportive care, including oxygen therapy and intensive monitoring, is critical for patients who develop severe respiratory distress[^26].Some strains have shown resistance to antiviral treatments. Therefore, New drugs and treatment protocols were developed [^27]. Ongoing research into the genetic evolution of these viruses is crucial to managing drug resistance[^28].

Global Health Impact Avian influenza has significant economic and public health implications. Outbreaks lead to massive culling of poultry, impacting economies reliant on poultry production[^29]. Human infections, though rare, pose a pandemic risk due to the potential for virus mutation, which could enhance transmissibility between humans[^30]. International health organizations such as the WHO, FAO, and OIE coordinate efforts to manage outbreaks, conduct surveillance, and promote vaccination campaigns. The Global Influenza Surveillance and Response System (GISRS) was created by WHO to monitor and respond to these outbreaks[^31].

Research and Future Directions Research is focused on understanding the mechanisms of avian influenza transmission and mutation. Efforts include developing new vaccines, creating antiviral drugs, and rapidly enhancing diagnostic capabilities to identify and contain outbreaks[^32]. Integrating the One Health approach addresses human, animal, and environmental health interconnectedness, which is essential in preventing future zoonotic transmissions[^33].

See Also - Influenza pandemics - Zoonotic diseases - One Health - Epidemiology of infectious diseases

References

1. World Health Organization (WHO). "Avian Influenza: Types and Outbreak Information." Available at: https://www.who.int. 2. Centers for Disease Control and Prevention (CDC). "Highly Pathogenic Avian Influenza." Available at: https://www.cdc.gov. 3. Webster, R. G., et al. "Evolution and ecology of influenza A viruses." *Microbiological Reviews* 56.1 (1992): 152-179. 4. Suarez, D. L. "Overview of Avian Influenza DIVA Test Strategies." *Biologicals* 33.4 (2005): 221-226. 5. Alexander, D. J. "An overview of the epidemiology of avian influenza." *Vaccine* 25.30 (2007): 5637-5644. 6. Capua, I., and Marangon, S. "Control of avian influenza in poultry." *Emerging Infectious Diseases* 12.9 (2006): 1319. 7. World Organisation for Animal Health (OIE). "Avian Influenza (Bird Flu)." Available at: https://www.oie.int. 8. Chen, H., et al. "The evolution and adaptation of H5N1 influenza virus in avian and human hosts in China." *Journal of Virology* 80.15 (2006): 7473-7482. 9. WHO. "Cumulative Number of Confirmed Human Cases for Avian Influenza A(H5N1) Reported to WHO, 2003-2023." Available at: https://www.who.int. 10. Yu, H., et al. "Human infection with avian influenza A H7N9 virus: an assessment of clinical severity." *The Lancet* 382.9887 (2013): 138-145. 11. Cowling, B. J., et al. "Prevention of avian influenza transmission in live bird markets in Hong Kong." *PLoS One* 3.4 (2008): e3055. 12. Gilbert, M., et al. "Mapping H5N1 highly pathogenic avian influenza risk in Southeast Asia." *Proceedings of the National Academy of Sciences* 105.12 (2008): 4769-4774. 13. CDC. "Protecting Against Avian Influenza (Bird Flu)." Available at: https://www.cdc.gov. 14. WHO. "Risk of human infection with avian influenza during outbreaks in animals." Available at: https://www.who.int. 15. Doyle, M. P., and Erickson, M. C. "Reducing the carriage of foodborne pathogens in livestock and poultry." *Poultry Science* 85.6 (2006): 960-973. 16. Munster, V. J., et al. "Human-to-human transmission of avian influenza A/H7N9 virus, China, 2013." *Clinical Infectious Diseases* 57.5 (2013): 812-814. 17. Beigel, J. H., et al. "Avian influenza A (H5N1) infection in humans." *New England Journal of Medicine* 353.13 (2005): 1374-1385. 18. Chen, Y., et al. "Human infections with the emerging avian-origin influenza A H7N9 virus from wet market poultry: clinical analysis and characterisation of viral genome." *The Lancet* 381.9881 (2013): 1916-1925. 19. WHO. "Clinical management of human infection with avian influenza A (H5N1) virus." Available at: https://www.who.int. 20. FAO. "Global Early Warning System (GLEWS) for Animal Disease Surveillance." Available at: https://www.fao.org. 21. WHO. "GISRS and Pandemic Preparedness." Available at: https://www.who.int. 22. Pantin-Jackwood, M. J., and Swayne, D. E. "Pathogenesis and pathobiology of avian influenza virus infection in birds." *Revue Scientifique et Technique de l'OIE* 28.1 (2009): 113. 23. Van den Berg, T., et al. "Vaccination strategies to prevent and control avian influenza." *Vaccine* 26 (2008): D8-D15. 24. WHO. "Reducing Risk of Transmission of Avian Influenza to Humans." Available at: https://www.who.int. 25. Moscona, A. "Oseltamivir resistance—disabling our influenza defenses." *New England Journal of Medicine* 353.25 (2005): 2633-2636. 26. Gao, R., et al. "Human infection with a novel avian-origin influenza A (H7N9) virus." *New England Journal of Medicine* 368.20 (2013): 1888-1897. 27. Ison, M. G. "Antiviral treatments." *Clinics in Laboratory Medicine* 34.2 (2014): 281-289. 28. WHO. "Influenza Virus Mutation and Drug Resistance." Available at: https://www.who.int. 29. Otte, J., et al. "Impacts of avian influenza virus on animal production in developing countries." *Developing Countries Initiative* 3 (2008): 1-52. 30. Taubenberger, J. K., and Morens, D. M. "Influenza: the once and future pandemic." *Public Health Reports* 125 (2010): 16-26. 31. WHO. "Global Influenza Surveillance and Response System (GISRS)." Available at: https://www.who.int. 32. Webster, R. G., and Govorkova, E. A. "H5N1 influenza—continuing evolution and spread." *New England Journal of Medicine* 355.21 (2006): 2174-2177. 33. Zinsstag, J., et al. "From ‘one medicine’ to ‘one health’ and systemic approaches to health and well-being." *Preventive Veterinary Medicine* 101.3-4 (2011): 148-156.