The Pharmaceutical Journal
Vol 275 No 7372 p502
22 October 2005

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Partially resistant avian flu virus isolated

An H5N1 strain of avian influenza virus that is partially resistant to oseltamivir (Tamiflu) has been isolated from a Vietnamese patient, according to a brief communication published in Nature this week (2005;437:1108).

Yoshihiro Kawaoka, University of Tokyo, and colleagues isolated the resistant virus from a girl who had been treated with a prophylactic dose of oseltamivir (75mg once daily for four days) after experiencing mild influenza symptoms. She was then given a therapeutic dose (75mg twice daily for seven days), after which no virus was isolated.

The researchers say that the girl had not had any known contact with poultry but had cared for her brother who had documented H5N1 virus infection. “The timing of infection in these two patients, together with the lack of known interaction of the girl with poultry, raises the possibility that the virus could have been transmitted from brother to sister,” they say.

The researchers identified a mutation in the virus strain’s neuraminidase protein that made it resistant to oseltamivir. However, assessment of the resistant virus in ferrets showed that the viral clones were still sensitive to zanamivir (Relenza). “[Our findings] raise the possibility that it might be useful to stockpile zanamivir as well as oseltamivir in the event of an H5N1 influenza pandemic,” they conclude.

David Salisbury, the Government’s head of immunisation for England, last week reassured the public that, despite cases of avian flu being confirmed in Turkey and Romania, “hardly anybody is at risk of catching avian flu from birds”. According to the World Health Organization, direct contact with infected poultry, or surfaces and objects contaminated by their droppings, is considered the main route of human infection.

In a press statement issued last week, the Health Protection Agency stressed that it remains important for people in at-risk groups to receive normal seasonal influenza vaccines. However, it highlighted that seasonal flu vaccine offers no protection against avian flu.