Hongkongers whose health is more vulnerable, such as the elderly, are urged to get their flu shots in the next week or so, after latest figures show Tamiflu-resistant flu is dominating the reported cases. Of 66 samples of influenza A tested, nearly 70 per cent were H1N1 Brisbane flu, a sub-strain of the virus that caused the 1918 Spanish flu pandemic, the most deadly in the past century. Thomas Tsang Ho-fai, the controller for the Centre for Health Protection, said last weekend that laboratory tests showed that 90 per cent of flu-like illnesses were caused by the H1N1 virus, which had been shown to be resistant to the antiviral Tamiflu in the US. Thomas Chung Wai-hung, who heads the centre's emergency response and information branch, said it also found that more than 90 per cent of the H1N1 Brisbane flu samples tested were Tamiflu-resistant. 'We are more or less comparable to the other places, that is, we have a relatively high proportion of Tamiflu-resistant H1N1 flu,' said Dr Chung. 'We are concerned too, having noted that this virus can mutate from time to time. That is why we monitor very closely the situation in Hong Kong as well as globally. 'We are aware that the resistant strain is circulating elsewhere.' Its prevalence meant doctors could not use Tamiflu to treat a person infected with the H1N1 flu strain, Dr Chung said. But he also noted that most flu cases needed only rest and symptomatic medication for treatment. Just 10 per cent of the 66 samples tested were of the H3N2 Brisbane strain, the same strain that caused the last flu pandemic, called Hong Kong flu, in 1968. Last year, H3N2 caused outbreaks in schools in Hong Kong and, this winter, it is slowly moving towards continental Europe after affecting Britain. The resistant strain has been found to respond to the inhalant drug Relenza, though Hong Kong is stockpiling more Tamiflu. Antivirals are effective when given within a few days of the symptoms. Dr Chung said no study had conclusively established why the H1N1 strain was resistant to Tamiflu. 'One of the characteristics of this virus [H1N1 Brisbane] is it mutates a little bit from time to time,' he said. The good news was that a vaccine could still protect the vulnerable from Tamiflu-resistant H1N1, he said. The flu season was expected to peak in three weeks, he said. The immune response does not kick in until two weeks after vaccination, and for young children receiving the flu shot for the first time, it will take four weeks for them to have full immunity because they need two shots two weeks apart. Percentage of H1N1 viruses resistant to Tamiflu: 90%+
