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Flu Pandemic Unpreparedness - Tamiflu Containment Myth
May 18, 2005
>> Scientists believe that if Tamiflu is quickly supplied at the site of an initial pandemic outbreak, it could help to contain the bug for as long as six months or even eliminate it. Six months is about what researchers would need to develop a vaccine based on the pandemic strain that emerges. <<
Although Tamiflu could contain H5N1, the available evidence suggests that this strategy is much more wishful thinking than a approach likely to succeed. Assuming the H5N1 infections in people could be quickly identified, which is a major assumption because H5N1 has been endemic to Vietnam for at least several years and there is no comprehensive survey of where it is and is not in humans, there would still be major bird flu containment issues.. A recent survey of ducks and chickens indicated H5N1 was in 71% of ducks and 21% if chickens in the Mekong Delta. Most of these infections were in asymptomatic birds and now evidence is emerging that pigs in Indonesia may be asymptomatically infected. It seems likely that pigs in Vietnam and Thailand are similarly infected,
In addition, Tamiflu was used to try to contain an H5N1 outbreak in tigers in a Sri Racha zoo in Thailand. Prophylactic treatment, combined with culling, failed to stop H5N1 and 147 tigers died or were euthanized, even though Tamiflu was used at double the recommended dose.
Possible H5N1 problems were forecast in in vitro assays. Tests of Tamiflu against all 9 N serotypes indicated that the drug could inhibit spread of the virus, but N1 was among the most resistant serotypes. Recent data with H5N1 again showed that Tamiflu could inhibit the virus, but even more drug was required. However, the supply of Tamiflu is limited.
However, it is the most recent report on treating humans known to be infected with H5N1 that raises a major red flag on use of Tamiflu to control or eliminate H5N1. Media reports suggest that Tamiflu resistance developed in one patient being treated with Tamiflu. The number of reported H5N1 human infections has been exceedingly low, so resistance in this group indicates antiviral resistance will be common. However, because it is possible that the number of non-hospitalized patients infected with H5N1 may be markedly higher than the reported cases, Tamiflu resistance in H5N1 may already be much more common than the one cited case.
Thus, stockpiling Tamiflu may make stockpilers feel that the supplies may limit or eliminated H5N1, but real data, although limited, suggest the containment plan, like the surveillance plan, is not reality based.