Summary and Comment
Two new studies document the characteristics of human H5N1 influenza in Turkey and of three clusters in Indonesia.
Summary
With the continuing pandemic of highly pathogenic H5N1 influenza in birds in Asia, Europe, and Africa, considerable concern remains that this influenza strain will jump species and cause widespread human infection. Given this concern, close attention is focused on human cases worldwide. Two teams of investigators now provide new insights.
Oner and colleagues report the clinical and epidemiologic features of 8 of the 12 cases of human H5N1 influenza infection noted in Turkey during the 2005-2006 winter season. When an outbreak of H5N1 influenza in poultry was recognized in eastern Turkey, surveillance for human cases was undertaken at the Yuzuncu Yil University Hospital. From December 31, 2005, through January 10, 2006, 625 patients were screened for H5N1 infection, and 290 of them underwent diagnostic testing. Eight had H5N1 infection, confirmed by the WHO. Infection was identified by an RT-PCR assay on nasopharyngeal secretions in four patients and by RT-PCR assays on lower respiratory tract samples in four individuals who had had negative nasopharyngeal assays but were retested due to severe illness. All eight patients were adolescents, and all shared living space with poultry. The incubation period was 4 to 7 days; all patients had fever; seven had clinical or radiologic evidence of pneumonia; and four (50%) died from 10 to 15 days after disease onset. Notable laboratory findings were leukopenia, lymphopenia, thrombocytopenia, and elevated serum aspartate aminotransferase, lactate dehydrogenase, and creatinine kinase levels.
Kandun and associates collected epidemiologic and clinical data on all human cases of H5N1 influenza infection in Indonesia and followed contacts for illness. In 2005, they identified three clusters of cases of H5N1 disease. The first cluster involved a father and two daughters who had had close physical contact with each other but no known contact with poultry, although an infected caged bird was found near their home. The second cluster involved a woman and her nephew who lived in close proximity to poultry. The third cluster involved two brothers and their nephew, who lived in a rural village where poultry had died. Five of these eight individuals died. Molecular sequencing of viral isolates from one patient each from the first two clusters showed that infection was caused by clade 2 H5N1 influenza.
Comment
The outbreak of H5N1 influenza in Turkey reaffirms that this pathogen is highly virulent and highlights potential difficulties in confirming the diagnosis. Rapid influenza assays and ELISA assays were negative in all cases; RT-PCR assays on lower respiratory secretions, not nasopharyngeal samples, appear to yield the most diagnoses. All these cases of human infection were due to a different clade of H5N1 influenza than the one that caused initial human disease in Southeast Asia. The relatedness of individuals in the clusters suggests that genetic factors may predispose to infection with this virus.
--- Richard T. Ellison III, MD
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Journal Watch. 2006;5(12) © 2006 Massachusetts Medical Society
Cite this: Updates on H5N1 - Medscape - Dec 06, 2006.
Comments