H5N1 Spread Into New Areas of West Bengal
Recombinomics Commentary 19:29
February 1, 2008
Three hundred chicks were reported dead at Baganbari village in Falakata area of Jalpaiguri
In Darjeeling where chicken deaths were reported from Takdah village on Thursday, district magistrate Rajesh Pandey said the report on the samples was still awaited and no culling was being carried out.
Darjeeling municipality announced a ban on the sale of chicken and poultry products and asked people to desist from consuming them.
In worst-affected Birbhum the work to destroy chicken was taken up at Rajapukur, a new area to be affected by the disease as well as in Suri municipal area, official sources said at Suri.
The above comments describe additional regions in West Bengal that have tested positive for H5N1, as well as new districts with excessive poultry deaths (see satellite map here and here). H5N1 has not been confirmed in Jalpaiguri or Darjeeling. However, there is little doubt that H5N1 is in the districts. H5N1 has been confirmed in southern Tibet, northern Bangladesh, as well as adjacent Cooch Behar. The lack of confirmed H5N1 in Jalpaiguri and Darjeeling is linked to a lack of testing.
West Bengal testing has been minimal and has trailed the H5N1 spread. Confirmation is by rapid tests which have a low sensitivity. As noted in the recent review in the New England Journal of Medicine, rapid tests have a sensitivity of approximately 25%. This 75% of H5N1 positive samples test negative. This low sensitivity can be somewhat overcome by increased testing, but instead the testing has been minimal, so areas have outbreaks after culling in the region has be completed because H5N1 is not initially detected in the adjacent regions.
The actions of adjacent governments reflect this shortcoming. Precautionary culling has been order for border regions in Nepal and Asaam, because of the large number of positives in West Bengal as well as excessive poultry deaths. In some areas, such as North 24 Parganas, there are no confirmed cases because initial tests were negative, but the excessive poultry and wild bird deaths signal H5n1 in the region, regardless of test results.
The minimal and negative testing extends to wild birds and suspect human cases. India has yet to announce H5N1 positive wild birds, even though large numbers of deaths are linked to H5n1 positive poultry, and wild birds have tested positive in adjacent regions in Bangladesh. Similarly, long range migratory birds in India spend spring and summer in China, Siberia, and Mongolia, where H5N1 has been detected since the spring of 2005, yet there still have been no reports of H5N1 in migratory birds. The negative results also extend to suspect human cases in 2006, raising additional questions about testing and transparency. Moreover, the recent confirmation of H5N1 in Pakistan, where human cases were reported late last year, also suggest there are human H5N1 infections in India.
Thus, the negative data in wild birds and suspect human cases remain causes for concern.
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