Thursday, October 20, 2011

Study finds larger households a risk in Indonesian H5N1 clusters

Study finds larger households a risk in Indonesian H5N1 clusters
Cluster outbreaks of H5N1 avian influenza (AI) in Indonesia involved larger households and more close relatives compared with isolated cases, according to a statistical analysis published in Clinical Infectious Diseases.

An international team of researchers analyzed data from 139 H5N1 outbreaks, of which 113 involved isolated cases and 26 were clusters. The outbreaks involved 177 total cases—159 laboratory confirmed and 18 probable. A cluster was defined as two or more cases associated with a specific setting, with disease onset within 2 weeks of each other. The average cluster size was 2.5 cases.

The team used logistic regression to assess risk factors for the outbreaks and found that clusters involved larger households and more blood-related contacts, especially first-degree relatives, compared with isolated cases. Risk factors for secondary case infection were being from 5 to 17 years old or 18 to 30, having direct exposure to sources of H5N1 virus, and being a first-degree relative of an index case. In fact, siblings were five times more likely to contract secondary cases than were other contacts. The authors conclude, "The study adds evidence that AI H5N1 infection is influenced by, and may even depend on, host genetic susceptibility."
Oct 19 Clin Infect Dis abstract

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