According to a new data presented at the InterScience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), Washington DC, Tamiflu (oseltamivir), an oral neuraminidase inhibitor (NAI), is found effective against human and avian H5N1 influenza virus.

These data are particularly important as avian influenza strains, such as H5N1, are considered by experts to be the most likely source of a pandemic strain, against which older antivirals are not effective. This highly pathogenic strain is currently circulating in Vietnam and Thailand, and is responsible for the deaths of more than 30 people since January, release from Roche said.

"These data add to previous studies by the WHO and the Centre for Disease Control and Prevention (CDC) in the US, and suggest that Tamiflu can be expected to be effective against any mutating influenza virus - which is the key to a pandemic," commented Professor John Oxford, St Barts and The London, Queen Mary's School of Medicine and Dentistry, London, UK. "Since antivirals such as Tamiflu can be stockpiled, we are in a strong position to ensure that we are prepared for the next pandemic - however, few governments have adequate stock. I urge governments to follow WHO guidance and ensure that stockpiles of antivirals are assembled in good time," he concluded.

"We realise how important it is for governments to have stockpiles of Tamiflu in place when an influenza pandemic hits as the production lead time is so long. In order to meet the needs of governments, we have taken steps to increase our manufacturing capacity, at risk, even though we haven't had many firm orders," commented William M. Burns, head of Roche's Pharmaceuticals Division.

Tamiflu is designed to be active against all clinically relevant influenza viruses. It works by blocking the action of the neuraminidase enzyme on the surface of the virus. When neuraminidase is inhibited, the virus is not able to spread to and infect other cells in the body, Roche says.

Most avian influenza viruses are not infectious to humans, but, should an avian and a human influenza virus co-infect a human or a pig, the virus strains can join, mutate and create a completely new virus, which may be transmissible from animals to humans and from humans to humans. Such a strain would be entirely new in composition, so vaccines developed and administered to date to protect humans during seasonal epidemics, would be ineffective against this new strain, leaving the population vulnerable to infection.