H5N1 Spread in Bangladesh

Commentary

H5N1 Spread in Bangladesh
Recombinomics Commentary 07:35
December 11, 2008

Stray cases of bird flu have recently been detected in Assam's Kamrup district, West Bengal and in several districts of Bangladesh which shares a vast border with West Garo Hills district.

The above comments from a Meghalaya alert indicate H5N1 in Bangladesh has spread beyond the confirmed outbreak described in an OIE report filed last month. That outbreak began in October on a commercial poultry farm, and additional outbreaks have not been reported. In contrast, H5N1 has recently rapidly spread across Assam and confirmed cases stretch from Chirang in the northwest to Dibrugarh in the northeast (see satellite map).

Although these recent confirmed outbreaks are unlikely to link directly to Bangladesh (the confirmed outbreak in Dibrugarg is more than 400 miles from the confirmed outbreak in Bangladesh or 200 miles from the nearest Bangladesh border - see updated map), they do suggest significant levels of H5N1 are circulating in the region. The Meghalaya alert also suggests that unreported H5N1 is also in West Bengal.

Last season H5N1 in West Bengal and Bangladesh were not extensively reported until January / February, but villagers in West Bengal indicated poultry began to die in December and there were rumors that unreported outbreaks in Bangladesh in the same time frame were widespread.

Recent alerts by West Bengal and Tripura claim that last year's outbreaks were linked to smuggling from Bangladesh, but the earlier outbreaks were associated with deaths of resident and migratory birds, as well as birds of prey, dogs, and jackals, which would likely spread H5N1, even after borders were sealed.

Therefore, additional outbreaks in Bangladesh are likely at this time, and such outbreaks are likely to increase as the temperature falls. These seasonal changes will to move the H5N1 to the south via migratory birds, and Calcutta has already issued an alert that focused on spread by wild birds.

In the past, H5N1 in West Bengal and Bangladesh has been the Qinghai strain (clade 2.2) and more detailed analysis has indicated the H5N1 in the region (Afghanistan, Pakistan, and India) has been the sub-clade 2.2.3.

Human cases have been reported in Pakistan and Bangladesh in association with outbreaks last year, although the human H5N1 sequences have not been released, which is also true for avian H5N1 from the outbreaks last season or this season.

Release of these sequences, as well as more information on the recent outbreaks cited above, would be useful.