Brussels, 05 Oct 2005
Experts in Hong Kong have warned that the human H5N1 strain of avian flu that surfaced in northern Vietnam this year is proving resistant to Tamiflu, the commercial brand of oseltamivir, a powerful antiviral drug widely considered the best chance of protecting the population.
Dr William Chui, an associate professor at Queen Mary Hospital in Hong Kong, has said that health authorities could no longer rely on Tamiflu. 'There are now resistant H5N1 strains appearing and we can't totally rely on one drug,' reports Reuters. Mr Chui also claimed that general viral resistance to Tamiflu is growing in Japan, where doctors routinely prescribe this drug to fight common human influenza.
Public health experts have urged drug manufacturers to make more effective versions of Relenza (zanamivir), an alternative antiviral that is also known to be effective in battling the feared H5N1. Relenza is inhaled. 'Manufacturers should think about producing an injectable form of Relenza because resistance to Tamiflu has been seen in Japan and Vietnam,' Mr Chui said. 'Also with injections, high doses can be given where necessary and onset time is a lot faster.'
A small Japanese independent study published last August already suggested that influenza viruses were becoming resistant to Tamiflu, and that the resistance may be more common than thought. In this study, 18 per cent of the child patients had Tamiflu-resistant influenza, said lead researcher Yoshihiro Kawaoka, a professor of virology, microbiology, and immunology at the University of Tokyo.
A Swiss manufacturer Roche Holdings AG spokesperson said that its own research had pointed to resistance being much lower in both children and adults. Roche also pointed out that this study included several children under one year old (Tamiflu is not approved for use in this age group), and that the Japanese patients 'may not have received an adequate dose of Tamiflu'.
Two further reports published recently in The Lancet medical journal also state that resistance to anti-flu drugs is growing worldwide. In places such as China, drug resistance has exceeded 70 per cent, suggesting that drugs such as amantadine and rimantadine will probably no longer be effective for treatment or as a preventive, reports The Times.
News of the virus's presence advancing towards Europe has prompted the EU to begin stockpiling antiviral drugs. Tamiflu was being stockpiled by countries as part of 'preparedness strategies'. However, the UK now believes that, due to the speed with which the flu virus mutates, the most effective medication would not been known until a pandemic arrived. Tamiflu is however still considered to be an effective option. On BBC Radio, Sir Liam Donaldson, Chief Medical Officer for England, said that contingency plans for the UK had not changed.
The Australian federal government has also stockpiled about four million doses of Tamiflu, rather than the alternative anti-viral drug, Relenza, based on medical advice. The US federal government has stockpiled Tamiflu for one million people.
Finland has informed pharmaceutical labs across Europe that it is seeking 5.2 million doses of a vaccine against the deadly bird flu, allowing it to protect its entire population. The Finnish government has asked its parliament to free 21 million euro for the purchase of stockpiles of the vaccine. Although Finland aims to stockpile enough vaccines to protect all Finns, authorities are not planning to start vaccinating the population until an epidemic has been declared. Finland experienced its first bird flu scare last month, when gulls appeared to show signs of the virus. The strain was later found to be harmless to humans.
Fears about the latest strain of bird flu triggering a new pandemic are real in spite of the fact that there is no evidence of human-to-human transmission of the avian flu H5N1 strain. So far, it has mainly infected humans who were in close contact with infected birds. But the virus needs to be under permanent monitoring in order to establish whether there are any genetic changes that could make it become more lethal and spread more rapidly.
In recent weeks, several countries have joined forces to coordinate preparation. The United States announced a new International Partnership on Avian and Pandemic Influenza at a World Summit in New York. On 7 and 8 November the World Health Organisation will host a meeting of all partners to coordinate the funding needed.