May 4, 2006 (CIDRAP News) – A new study suggests that the antiviral drug oseltamivir (Tamiflu) can prevent deaths in ferrets infected with H5N1 avian influenza, according to reports today from an avian flu conference in Singapore.

News of the study"e;s findings came as the World Health Organization (WHO) reported Egypt"e;s 13th human case of H5N1 illness.

The oseltamivir study was reported at a 2-day meeting sponsored by the British journal The Lancet. In the experiment, a group of ferrets was infected with H5N1 and, 4 hours later, was given half the oseltamivir dose recommended for humans, according to an Associated Press (AP) report. Treatment continued for 5 days.

A second group of ferrets received a higher dose of oseltamivir starting 24 hours postinfection. All of the treated ferrets survived, while none of the untreated animals did, the AP reported. Elena Govorkova, MD, PhD, of St Jude Children"e;s Research Hospital in Memphis, presented the findings.

Oseltamivir has been widely touted as one of two neuraminidase inhibitors that show the most promise in fighting H5N1, and countries worldwide are stockpiling the drug in the face of a potential flu pandemic. However, its effectiveness against avian flu in humans is unknown, and Govorkova"e;s research is designed to help predict optimal dosing for humans in the event of a pandemic, according to Roche, the manufacturer of Tamiflu.

Ferrets provide good models for testing, because they are very susceptible to influenza and experience symptoms similar to humans when infected.

In Egypt, the avian flu patient is a 27-year-old woman who had recently visited a house where many chickens were slaughtered. Tests conducted by both the national public health laboratory and the Cairo-based US Naval Medical Research Unit 3 produced positive results for H5N1, according to the WHO.

The woman was admitted to a hospital with bilateral pneumonia on May 1 and is reported to be in stable condition. Hers is the first confirmed case in Egypt since early April, the WHO said.

The case brings the WHO"e;s worldwide avian flu tally to 206, including 113 deaths.

In other developments, an expert at the Singapore conference today said people infected with the H5N1 strain may possess genetic susceptibility, according to a Reuters report.

Among the 205 people reported infected since late 2003, there have been family clusters of blood relatives, such as father or mother and children. "So there has to be certainly a genetic aspect to it," said Robert Webster, PhD, of St Jude Children"e;s Research Hospital, as quoted by Reuters.

Hiroshi Kida, DVM, PhD, director of the Research Center for Zoonosis Control at Hokkaido University in Japan, said there have been no case clusters involving husband and wife, which increases the suspicion of a genetic role.

Kida offered a possible explanation, according to Reuters. He said that people infected with H5N1 have a carbohydrate receptor—alpha 2,3—lining their throats. This receptor is predominantly found in birds, and avian flu viruses bind to this class of receptor. Human flu viruses usually bind to a receptor called alpha 2,6, which is dominant in humans, he said.

Kida emphasized, however, that other explanations of why the avian flu virus does not as yet transmit easily between humans—such as the theory that it lodges deep in the lungs—may also be tenable.