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Suspect H5N1 Clusters in Surabaya Raise Pandemic Concerns
May 21, 2006
The recent reports of suspected H5N1 bird flu cases in Surabaya is cause for concern. The index case has been confirmed and died May 12. Her child is currently hospitalized with bird flu symptoms and an unrelated patient has also just died.
Although only one case has been confirmed, two additional suspect cases have raised additional concerns. One fatal infection is of a teacher, and one of her students has been hospitalized and is on a respirator.
The teacher decribed earlier appears to be another media description of the confirmed fatality (38M) and therefore there is no infected teacher and no relationship between a fatally infected teacher and the H5N1 confirmed student.
Transmission of H5N1 outside of a family has been rare. In Vietnam one confirmed transmission chain involved an index case, his sister, and a nurse, all of whom were H5N1 confirmed. A second nurse had symptoms, but was not confirmed in lab tests. However, the vast majority of clusters have been limited to family members. There was a large cluster in Turkey at the beginning of 2006, and more recently the largest Indonesian cluster, in North Sumatra. However, all members of these cluster were related to the index case.
The cluster involving teacher and student has not been reported previously. Such transmission would signal an increased efficiency and diminish the likelihood that the familial clusters were genetically linked. An earlier cluster of five in Haiphong involved a husband and wife and three daughter. All five family members were H5N1 confirmed and the infection of both husband and wife diminishes the genetic link. The results of tests on neighbors with symnptoms has been withheld.
Concerns that transmission is from a source other than avian has been raised since almost all sequenced human cases in West Java have a novel cleavage site not found in poultry isolates. This novel sequence has also been found in a cat, raising the possibility that the sequence is closely linked to mammalian infections.
Since most suspect cases in Indonesia are not tested in the absence of a poultry link, many infections from a mammalian source many not be diagnosed. The frequent detection of the novel cleavage site highlights the need for more aggressive testing of avian and swine H5N1 infections.
Similarly, the H5N1 human and animal sequences sequestered at the WHO private data base should be released immediately.