Salma Khalik, Straits Times 23 Feb 09;
BANGKOK: The rapid resistance of the flu virus against Tamiflu, a popular influenza medicine, has 'stunned' experts.
Several speakers at the 11th symposium on respiratory viral infections expressed their grave concerns over this.
First seen in the winter of 2007, the resistance to the drug in many countries in Europe, as well as the United States and Australia, was almost complete for the H1N1 strain of flu by early this year.
The implications, the experts said, are serious. It might mean that the huge stockpiles of this medicine that countries around the world have been building up, could be virtually useless should there be a bird flu pandemic.
Singapore has more than one million courses of this medicine, and is getting a further 650,000. Other countries have also been buying and keeping large amounts of Tamiflu on the advice of the World Health Organisation.
The medicine is meant for use against the anticipated next flu pandemic - with the bird flu or H5N1 virus as a current front runner for this major health disaster. Previous pandemics have killed millions of people.
Tamiflu, an antiviral, can be used to prevent a flu attack if taken daily, or to ameliorate the severity of the attack with two daily doses for five days. It has 90 per cent of the market for flu medication.
Dr Tawee Chotpitayasunondh, a specialist in infectious diseases with Thailand's Queen Sirikit National Institute of Child Health, said that resistance in Thailand built up from zero at the start of last year to 75 per cent by the end of the year.
This has spurred the Thai government to provide, for the first time, two million free flu vaccines for the elderly, very young and the sick who are more likely to suffer badly if they get the flu.
Professor Yoshihiro Kawaoka of the University of Wisconsin-Madison, whose work in 'reverse genetics' is now used in new generation flu vaccines, said that similar resistance has surfaced among a small number of people with bird flu. 'New flu drugs are needed,' he pointed out.
Professor Frederick Hayden of the University of Virginia School of Medicine, a member of WHO's global influenza programme till last August, said that up to 25 per cent of H5N1 victims are now resistant to Tamiflu. 'There is persistent replication of the virus with fatal outcomes.'
However, it is not all gloom and doom on the flu front. Another antiviral, Relenza, remains effective.
Dr Jennifer McKimm-Breschkin, who gave a closed-door presentation to about 30 policymakers from several countries, including Thailand and Vietnam, told The Straits Times that her advice is to keep 'a balanced stock of both medicines'.
The researcher from Australia's Commonwealth Scientific and Industrial Research Organisation said the two drugs are very different, although both inhibit the virus from reproducing.
Relenza is inhaled and works extremely well if the virus only replicates in the airways, since that is where the drug is mostly concentrated.
Tamiflu, on the other hand, is swallowed, is dispersed throughout the body and is good to stop the virus if it also replicates in other organs.
But change in the inhibiting factor needed to make Tamiflu into a capsule that can be taken orally is also the reason it allows resistance. This does not happen with Relenza, which should continue to work with all flu types.
Singapore has 50,000 courses of Relenza as part of its anti-flu arsenal.
Dr McKimm-Breschkin said that influenza viruses generally replicate in the airways, but some people fear this might change in future.
Tamiflu would remain useful if the pandemic is caused not by bird flu but by a different flu strain.
