H5N1 Virus Detected in Some Dead Animals
Concerns Over Infection of Zoo Staff in Direct Contact
Recently, over 50 tigers, lions, and leopards housed in a Vietnamese zoo died in a mass mortality event, with some found to be infected with the highly pathogenic avian influenza A virus (H5N1), causing local health authorities to be on high alert.
On the 3rd (local time), local media including VN Express reported that since August until now, 44 tigers, 3 lions, and 1 leopard have died in mass at the 'Mango Garden' Zoo in Dong Nai Province and the 'Mikun' Zoo in Long An Province in southern Vietnam. Before dying, the animals showed symptoms of fatigue and weakness, and autopsies conducted by quarantine authorities detected the H5N1 virus in some of the carcasses.
H5N1 is a highly pathogenic type of avian influenza A virus, commonly known as "bird flu." It infects poultry such as chickens and ducks through contact with migratory birds, but contrary to its name, it is not a disease that only infects birds. Other mammals such as lions, tigers, dogs, and cattle are also at risk of infection. In particular, H5N1 is known for its rapid mutation and ease of transmission to other animals.
Vietnamese authorities have deployed quarantine personnel to the two zoos to inspect the sites and begin disposing of the deceased animals. Although the exact infection route has not yet been identified, there is speculation that the virus may have spread through transactions between the two zoos. It was found that three tigers that died at Mikun Zoo were brought in from Mango Garden Zoo in early last month without proper quarantine certificates.
Since H5N1 has the potential to infect humans, the Vietnamese government is taking measures to prevent the worst-case scenario of the virus spreading to people. Currently, it is understood that 30 employees from Mango Garden Zoo and 3 employees from Mikun Zoo had direct contact with the deceased animals; however, none of them have shown respiratory symptoms.
So far, cases of avian influenza infecting humans have been rare, but the mortality rate for humans infected with avian influenza is known to exceed 50%. According to overseas reports of human infections, among 902 people infected with H5N1, 466 died, resulting in a fatality rate of 51.7%.
Because of this, some predict that avian influenza could lead to the next pandemic after COVID-19. Robert Redfield, former director of the U.S. Centers for Disease Control and Prevention (CDC), expressed concern about the mortality rate of highly pathogenic avian influenza when transmitted to humans, stating, "It is significant even compared to COVID-19. It will likely have a fatality rate between 25% and 50%," and warned, "A highly pathogenic avian influenza pandemic is a matter of time."
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