Ring prophylaxis for H1N1 influenza outbreaks

January 01, 0001

Ring prophylaxis for H1N1 influenza outbreaks

These authors from Singapore report the efficacy of ring chemoprophylaxis (geographically targeted containment by means of prophylaxis) with oseltamivir to control outbreaks of 2009 H1N1 influenza in semiclosed environments. All personnel with suspected infection were tested and clinically isolated if infection was confirmed. In addition, they administered postexposure ring chemoprophylaxis with oseltamivir and segregated the affected military units to contain the spread of the virus. All personnel were screened three times weekly both for virologic infection, by means of nasopharyngeal swabs and reverse-transcriptase-polymerase-chain-reaction assay with sequencing, and for clinical symptoms, by means of questionnaires.

They found: "A total of 1175 personnel were at risk across the four sites, with 1100 receiving oseltamivir prophylaxis. A total of 75 personnel (6.4%) were infected before the intervention, and 7 (0.6%) after the intervention. There was a significant reduction in the overall reproductive number (the number of new cases attributable to the index case), from 1.91 before the intervention to 0.11 after the intervention. Three of the four outbreaks showed a significant reduction in the rate of infection after the intervention. Molecular analysis revealed that all four outbreaks were derived from the New York lineage of the 2009 H1N1 virus and that cases within each outbreak were due to transmission rather than unrelated episodes of infection. Of the 816 personnel treated with oseltamivir who were surveyed, 63 (7.7%) reported mild, nonrespiratory side effects of the drug, with no severe adverse events."

The authors concluded: "Oseltamivir ring chemoprophylaxis, together with prompt identification and isolation of infected personnel, was effective in reducing the impact of outbreaks of 2009 H1N1 influenza in semiclosed settings."

This approach may be useful in other settings and with other diseases with similar mode of transmission.

For the full abstract, click here.

N Engl J Med 362(23):2166-2174 10 June 2010
© 2010 to the Massachusetts Medical Society
Oseltamivir Ring Prophylaxis for Containment of 2009 H1N1 Influenza Outbreaks. Vernon J. Lee, Jonathan Yap, Alex R. Cook, et al. Correspondence to Dr. Lee: vernonljm@hotmail.com

Category: R. Respiratory. Keywords: H1N1, influenza, prevention, oseltamivir, military units, semi- closed environments, before-and-after study, journal watch.
Synopsis edited by Dr Linda French, Toledo, Ohio. Posted on Global Family Doctor 22 June 2010

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