Experts Assess First Human H5N5 Case as Isolated Incident

The recent death of a person in the United States due to the H5N5 avian flu has raised concerns, but experts in Taiwan deem the case an isolated incident. They assert that the likelihood of wider transmission remains low. This assessment follows the confirmation by U.S. health authorities last week regarding the fatality caused by a strain of the flu that had not previously been known to infect humans.

According to Chao Day-yu, a professor at the National Chung Hsing University (NCHU) Graduate Institute of Microbiology and Public Health, the infection likely occurred through a spillover pathway involving wild birds, poultry, and finally humans. She emphasized that such sporadic cases generally have a minimal chance of escalating into a pandemic.

The H5N5 virus is part of a broader family of avian influenza strains, which have occasionally caused human infections. Historically, only a few subtypes, such as H5N1, which led to an outbreak in Hong Kong in 1997, and H7N9, confined to China, have significantly impacted human health. While other subtypes have been detected among humans, there have been no indications of human-to-human transmission.

Growing Vigilance Required

Despite the low probability of widespread transmission, Chao highlighted a worrying trend: avian influenza viruses are increasingly spilling over into various animal hosts, including carnivorous wildlife and marine animals. This trend necessitates heightened vigilance and preventive measures, she noted.

NCHU distinguished professor Chang Poa-chun contributed further insights, clarifying that seasonal human influenza viruses do not simply evolve into avian strains when transmitted to birds. The transformation of viruses requires a long-term, multistep evolutionary process.

Avian influenza viruses belong to the category of influenza A, which also includes other animal-originated strains circulating in poultry and livestock. Any human infection with these non-seasonal strains is classified as a novel influenza A case, categorized in Taiwan as a Category 5 notifiable infectious disease. This classification emphasizes the importance of tracking and managing such infections to prevent potential outbreaks.

In conclusion, while the H5N5 case in the United States is concerning, experts in Taiwan remain confident that it is an isolated event. The research community continues to monitor avian influenza closely, ensuring that necessary precautions are in place to safeguard public health.