Importance of measures against the threat of avian influenza virus mutation in infected hosts

Since January 2023, in Japan, outbreaks of infection with avian influenza viruses have had a major impact on the survival of wild birds. So far, avian influenza viruses rarely infect humans. However, viruses can mutate rapidly. Different strains of virus can exchange genetic sequences with each other in vivo in the infected host. Therefore, genetically-recombined viruses may survive in various environments and spread infection. Previous studies have shown that avian influenza viruses can infect a wide variety of mammals, including cats, foxes, otters, seals and sea lions.

If a new virus variant acquires high infectivity in mammals, including humans, it is conceivable that the infection will spread from mammal to mammal. In 2020, at mink farms in Denmark and Spain, SARS-CoV-2 infected mink from keepers, causing an outbreak of SARS-CoV-2 among farmed mink (1). Furthermore, SARS-CoV-2 mutated in vivo in cultured mink, becoming a new SARS-CoV-2 variant and infecting keepers. At this time, there was concern that in vivo mutated SARS-CoV-2 variants in cultured mink might escape from the antiviral immunity induced by COVID-19 vaccination.

According to a survey up to February 2023, it has been reported that the infection of avian influenza virus in farmed mink is also spreading in mink farms in Spain. And avian influenza viruses have been confirmed to infect humans in small numbers from mink. In other words, it is conceivable that the avian influenza virus mutated in vivo in cultured mink, resulting in the generation of a new avian influenza virus variant capable of infecting humans.

Countermeasures against infection of mammals with avian influenza viruses are being considered in each country. In April 2022, a dead Ezo red fox and a weakened raccoon dog by infection with the avian influenza virus were found, becoming the first case of avian influenza virus infection in a mammal in Japan. Ezo red foxes and raccoon dogs probably preyed on wild birds infected with the avian influenza virus, which is thought to be the cause of the infection of mammals with the avian influenza virus.

Eradication of wild birds and poultry raising infected with the avian influenza virus will prevent the epidemic of the avian influenza virus among mammals. In the 2022-2023 season, more than 12 million egg-laying hens have already been infected with avian influenza in Japan. As a result, about 10 million egg-laying hens have been culled. The number of culled egg-laying hens is about 9% of all hens raised in Japan. The Japanese government must provide financial support to poultry farmers.

1. Hayashi T, et al. Highly conserved binding region of ACE2 as a receptor for SARS-CoV-2 between humans and mammals. Veterinary Quarterly. 2020 Dec;40(1):243-249.

We do not have potential conflicts of interest.

Doctor specializing in cancer care / Doctor specializing in emerging infectious diseases.

Published on February 23, 2023 by Kyoto@takumaH