21-07-2025
Researchers: Delayed treatment of bird flu may raise risk of drug-resistance
A group of researchers says delayed treatment of a type of bird flu now spreading on dairy farms in the United States may increase the virus's drug-resistance.
The group is led by Professor Kawaoka Yoshihiro of the University of Tokyo Pandemic Preparedness, Infection and Advanced Research Center.
It has been studying the highly pathogenic H5N1 avian influenza virus that has spread rapidly among US dairy cattle since early 2024.
There have been reports that the virus appears to have been transmitted from cows to humans in 41 cases.
The researchers gave the antiviral drug Xofluza, or baloxavir marboxil, to mice infected with bovine H5N1 virus and examined its efficacy.
They say that of the five mice treated with Xofluza from 24 hours after infection, three died within 21 days. They say a Xofluza-resistant virus was found in one dead mouse.
The researchers say all five mice that were given Xofluza from 48 hours after infection died. Three of them reportedly had drug-resistant viruses.
But the group says none of the mice given the drug starting one hour after infection died, and no drug-resistant viruses were found in them.
Professor Kawaoka says there is a possibility that the virus multiplies so quickly that the emergence of drug-resistance might be facilitated.
He says there is need to explore ways to respond, such as extending the period of drug administration and increasing dosage, in case humans are infected.
