Increasingly, indications are that the H1N1 influenza might pose a greater health threat than we saw with the recent pandemic.
There are two reasons to think this. First the World Health Organization is receiving reports that Tamiflu-resistant H1N1 strains are popping up around the world. The Canadian Press reports that Japan has found three cases of Tamiflu resistance, while Canada, Denmark, Hong Kong and Singapore each discovering one. China reportedly also has seen Tamiflu-resistant H1N1. The big unknown is whether the resistant pandemic-causing virus swapped genes with last year’s seasonal flu virus for which Tamiflu was declared all but useless. If the pandemic flu picks up those resistance genes, it could render government stockpiles of the drug much less effective for treating severe cases or slowing the spread of the virus.
Tamiflu, which is manufactured by Roche, is the first line defense for influenza, especially the H1N1 strain since there is no vaccine for it–yet. Obviously, an effective vaccine will minimize the need for Tamiflu, but, while several vaccines are being tested, the big question is whether we will have an effective one in sufficient quantity for this winter’s flu season. We will continue to rely on Tamiflu until an effective vaccine is available. In the current absence of an H1N1 vaccine, it will be interesting to see how the virus affects the Southern hemisphere, which is now in the middle of its flu season. I suspect that we can expect more Tamiflu-resistant H1N1 sub-strains appearing below the equator in short order.
More troubling, however, is that the relatively mild virus that caused last winter’s pandemic may be nastier than originally suspected. A recent study, led by University of Wisconsin-Madison virologist, Yoshihiro Kawaoka, provides surprising insight of the pandemic virus and its pathogenic qualities, according to a press release from the university.
In contrast to run-of-the-mill seasonal flu viruses, the H1N1virus infects and replicates in cells deep in the lungs, which increases the chance of pneumonia and death. Seasonal viruses typically infect only cells in the upper respiratory system.
Kawaoka and his colleagues infected mice, ferrets and non-human primates – all widely accepted models for studies of influenza – with the pandemic virus or with a seasonal flu virus for comparison. They found that the H1N1 virus replicates much more efficiently in the respiratory system than seasonal flu and causes severe lesions in the lungs similar to those caused by other more virulent types of pandemic flu viruses. In contrast, the seasonal virus did not replicate in the lungs.
The ability of H1N1 to infect deep in the respiratory system is reminiscent of other pandemic flu viruses, notably the 1918 virus, which killed tens of millions of people at the tail end of World War I.
The good news, however, is that several H1N1 vaccines are currently being tested for safety and efficacy. It is encouraging that the testing centers have reportedly been inundated with volunteers willing to test the vaccine, so it doesn’t appear that volunteer recruitment will hold up the testing and development of an effective vaccine.
The race is on.
Recent columns by Steve Clark
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