Bird Flu Clusters in Thai Binh May Signal Change - WHO
Recombinomics Commentary
March 14, 2005
>> The main concern of the WHO was a series of cases of the deadly H5N1 bird flu virus in a family in the northern Vietnam province of Thai Binh and the possible infection of two nurses who cared for one of the patients.
It also said it had received confirmation of an additional 10 cases of human infections from Vietnam's Health Ministry.
"Full information on new cases, including those that may be closely related in time and place, is critical to ongoing assessment of the pandemic risk posed by the H5N1 virus," the U.N health agency said in a statement.
The new cases were detected in early March or through re-examination of older cases, some of which dated back to late January and three of which had been fatal, the WHO said. <<
The acknowledgement by the WHO of the importance of time and place in analyzing H5N1 is important. It is precisely the bimodal distribution of disease onset dates in cases within familial clusters that clearly show human-to-human transmission.
The number of familial clusters has been increasing recently and they account for over one third of reported cases in Vietnam, Thailand, and Cambodia. Recently, the familial clusters have been enhanced by a geographic cluster in Thai Binh, raising additional concerns.
Adding one or two health care workers to the familial cluster extends the cluster in time, and also signals a more efficient human-to-human transmission.
A changing demographic in cases in the northern and southern positions of Vietnam was noted in January. As patients in the north began to recover, the two populations became less similar. As the case fatality rate began to drop in the north, it remained at 100% in the south.
Notifications to the WHO from Vietnam had stopped in late January, and recent updates provided additional information for the WHO update. However, this news blackout remains in place for new human infections in the south. This lack of information is of concern because of reports of false negatives in the south as well as antigenic drift in one of nine sequenced isolates. There have been no specific reports on sequences from the north, other than general comments about antigenic drift and cases becoming complex.
Thus, at a time when H5N1 appears to be changing the most, crucial data are being withheld, increasing the likelihood of a major pandemic that is not detected and monitored until it is clearly beyond control.
Media link