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Mild H5N1 in Aswan Egypt
March 26, 2007
The case is a female child, three years old. The illness started on the 22nd of March and admitted to the hospital on the 24th where they put her on tamiflu. The samples were taken on the 24th and confirmed positive for H5N1 on 25 March 2007. The patient had a history of contact with backyard poultry. The patient is still in a good health condition and is not epidemiologically linked to the previous two human cases in Aswan.
The above comments (emphasis added) from the WHO Eastern Mediterranean Regional Office supports media reports indicating the three confirmed H5N1 cases in Aswan were mild. Media reports indicate the two earlier cases (10F and 2M) were briefly hospitalized and have been discharged. The above comments indicate the most recent case “is still in a good health condition.” These comments support media reports indicating that the patients had a high fever and “cold” symptoms. None of the reports indicated the patients developed pneumonia, and the short hospital stay supports a mild presentation.
The descriptions are similar to earlier reports in 2005 on cases in central and northern Vietnam. These earlier re[ports included 195 suspect cases in central Vietnam as well as a family of five in Haiphong. All five family members developed symptoms at the same time, were H5N1 confirmed, and were briefly hospitalized. Although serum samples from these patients were tested repeatedly in Vietnam, the United States, and Japan, there was no official reports on the conflicting test reports. Media reports indicated positive results were seen by the CDC in the United States as well as Hanoi.
The three cases in Aswan were hospitalized within nine days of each other and confirmed to be H5N1 positive. However, it seems likely that the number of cases in Aswan could be markedly higher, since the symptoms appear to be similar to those of a bad cold, and many patients with such symptoms would not seek medical attention or be tested.
Like Vietnam, the milder cases were associated with a change in the HA cleavage site. In northern Vietnam in 2005, the cleavage site lost an R, changing from RERRRKKR to RERRKKR. In Aswan in southern Egypt, the Qinghai HA cleavage site changed a K to an R resulting in GERRRRKR from GERRRKKR. In both instances the new cleavage site had been reported earlier in birds, and in each case the previously reported cleavage site appeared on a regional specific genetic background.
In Egypt, the altered cleavage site was also associated with reassortment. The NA sequence in southern Egypt is almost identical to sequences from fatally infected patients from central Egypt. However, the HA sequences in central and southern Egypt were readily distinguished. The cases in the north had a 3 nucleotide deletion and the consensus Qinghai cleavage site, while the cases in the south had no deletion, but had the novel cleavage site which had been previously reported in swans in Mongolia.
The presence of a lethal H5N1 in central Egypt, and a mild H5N1 in southern Egypt is cause for concern. Mild cases of H5N1 are more likely to be transmitted because the host is more mobile and cold symptoms are not as alarming as severe flu symptoms followed by pneumonia. The altered cleavage site may increase transmission, as evidence by three confirmed cases in nine days. Thus far there are no reports of H5N1 in contacts, but detection may be linked to high fevers, and lower levels of H5N1 may produce milder symptoms which may limit testing and/or detection. Therefore, increased efficiency of infection may not be evident.
Antibody testing of contacts with these children would be useful.
Co-circulation of an efficiently transmitted H5N1, with a highly lethal H5N1 could result in further recombination and/or reassortment to produce an efficiently transmitted lethal Qinghai H5N1.