Oseltamivir rings can slow rate of H1N1 outbreak

Oseltamivir ring prophylaxis helped slow down H1N1 influenza outbreaks in Singapore military camps in 2009, according to the results of a study reported in the June issue of the New England Journal of Medicine.

Vernon J. Lee, a researcher from the National University of Singapore, reported there were four cases of H1N1 between June 22 and June 25 in Singapore military camps.

“We 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,” Lee said in the study.

Lee said all people suspected of having the H1N1 infection were tested. Meanwhile, those who had been positively identified as having the virus were clinically isolated. To keep H1N1 from spreading, postexposure ring chemoprophylaxis with oseltamivir was used, with affected military units segregated.

“Screening was performed three times weekly, using nasopharyngeal swabs and reverse-transcriptase polymerase chain reaction assay with sequencing for all personnel,” Lee said, the New England Journal of Medicine reports.

Additionally, questionnaires were used to determine clinical symptoms.

Approximately 1,100 of 1,175 soldiers at risk of having the infection received oseltamivir prophylaxis, according to the study. Infection occurred in 75 personnel - 6.4 percent - before the intervention was used but only in seven people - 0.6 percent - after the intervention, thus showing postintervention rates of infection declined significantly in three of the four outbreaks.

“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,” the authors of the study concluded. “The use of oseltamivir prophylaxis as a containment measure may be limited to semiclosed or closed communities, since transmission in communities in the general population may subsequently lead to further outbreaks.”