It is hoped that, at best, Tamiflu may help avian flu victims in the first few days after catching the virus. It is specifically designed to treat symptoms of influenza A and B viruses. Nevertheless, while avian flu is an influenza A virus, each type has numerous subgroups that are determined by HA (haemagglutinin) and NA (neuraminidase) proteins. Altogether, there are 16 HA subtypes and nine NA subtypes, so an influenza A virus can have a unique chemical profile that makes it difficult to counteract with drugs.

More worrying is the safety profile of Tamiflu. The Japanese health authorities have reported that, so far, eight people have died after being given Tamiflu. Dr Rokuro Hama, head of the Japan Institute of Pharmaco-Vigilance, says that all of the victims have been children and adolescents between two and 17 years of age.

Two of the victims were teenage boys who behaved abnormally after being given the drug, said Chugai Pharmaceuticals, Tamiflu’s distributor in Japan, according to an online website (SABCNews.com). Earlier this year, a 14-year-old boy, after taking one Tamiflu capsule, jumped or fell from the ninth floor of an apartment building. In another case from last year, a 17-year-old boy left his home during a snowstorm, and jumped in front of a truck and died after taking the drug. Doctors say that, in both these cases, the boys had not exhibited any abnormal behaviour before taking the drug.

In addition, Japan’s health ministry has received reports of 64 cases of psychological disorders associated with the vaccine over the past four years.

This is not the first health alert for this drug. In 2003, the Food and Drug Administration (FDA), America’s drugs regulator, issued an alert that Tamiflu might be dangerous if taken by children younger than one year old. Following this warning, Roche issued a letter that instructed doctors not to prescribe the drug to very young children as animal studies had suggested that it could be fatal.

Both these reports are worrying developments for a drug that Roche had consistently maintained is ‘well tolerated’. Side-effects were thought to be relatively benign and transitory, and include nausea and vomiting. Other effects that have been regularly reported include diarrhoea, bronchitis, stomach pain, dizziness and headache.

Tamiflu shouldn’t be taken by anyone with kidney or liver disease, or any chronic condition. Pregnant women and breastfeeding mothers are also not advised to take the drug as there are insufficient data from human studies to determine its safety.

Furthermore, although it is regularly given to children and adolescents, its safety has never been established in children younger than 18 years of age as a flu treatment, or among 13-year-olds as a preventative.