On the military training facility of Tekong Island, Singapore, a comprehensive vector-borne disease control program was started in end-2006 to reduce mosquito populations and negate the need for anti-malaria chemoprophylaxis. The program was based on 1) preventing importation of malaria through screening of visitors, 2) preventing human-to-mosquito transmission through early case detection and mosquito control, 3) preventing mosquito-to-human transmission through personal protection, and 4) contingency plans. Systematic environmental works were performed to reduce breeding sites, and insecticide use targeted both adult mosquitoes and larvae. Mosquito populations declined from 103 mosquitoes per sampling site in January 2007 to 6 per site by March 2007 (P < 0.001). The proportion of positive ovitraps declined from 93% in January 2007–2% in March 2007 (P < 0.001). There were no malaria cases on the island despite chemoprophylaxis termination, showing that comprehensive combination vector-control strategies were effective in reducing the risk of malaria.
Background. Few studies have validated the effectiveness of public health interventions in reducing influenza spread in real-life settings. We aim to validate these measures used during the 2009 pandemic. Methods. From 22 June to 9 October 2009, we performed a prospective observational cohort study using paired serum samples and symptom review among 3 groups of Singapore military personnel. "Normal" units were subjected to prevailing pandemic response policies. "Essential" units and health care workers had additional public health interventions (eg, enhanced surveillance with isolation, segregation, personal protective equipment). Samples were tested by hemagglutination inhibition; the principal outcome was seroconversion to 2009 influenza A(H1N1). Results. In total, 1015 individuals in 14 units completed the study, with 29% overall seroconversion. Seroconversion among essential units (17%) and health care workers (11%) was significantly lower than that in normal units (44%) (P < .001). Symptomatic illness attributable to influenza was also lower in essential units (5%) and health care workers (2%) than in normal units (12%) (P = .06). Adjusted for confounders, unit type was the only significant variable influencing overall seroconversion (P < .05). From multivariate analysis within each unit, age (P < .001) and baseline antibody titer (P = .012) were inversely related to seroconversion risk. Conclusions. Public health measures are effective in limiting influenza transmission in closed environments.
Background. Few studies have validated the effectiveness of public health interventions in reducing influenza spread in real-life settings. We aim to validate these measures used during the 2009 pandemic. Methods. From 22 June to 9 October 2009, we performed a prospective observational cohort study using paired serum samples and symptom review among 3 groups of Singapore military personnel. "Normal" units were subjected to prevailing pandemic response policies. "Essential" units and health care workers had additional public health interventions (eg, enhanced surveillance with isolation, segregation, personal protective equipment). Samples were tested by hemagglutination inhibition; the principal outcome was seroconversion to 2009 influenza A(H1N1). Results. In total, 1015 individuals in 14 units completed the study, with 29% overall seroconversion. Seroconversion among essential units (17%) and health care workers (11%) was significantly lower than that in normal units (44%) (P < .001). Symptomatic illness attributable to influenza was also lower in essential units (5%) and health care workers (2%) than in normal units (12%) (P = .06). Adjusted for confounders, unit type was the only significant variable influencing overall seroconversion (P < .05). From multivariate analysis within each unit, age (P < .001) and baseline antibody titer (P = .012) were inversely related to seroconversion risk. Conclusions. Public health measures are effective in limiting influenza transmission in closed environments.
Background: From June 22 through June 25, 2009, four outbreaks of infection with the pandemic influenza A (H1N1) virus occurred 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. Methods: All personnel with suspected infection were tested and clinically isolated if infection was confirmed. In addition, we 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. Results: 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 (95% credible interval, 1.50 to 2.36) before the intervention to 0.11 (95% credible interval, 0.05 to 0.20) 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. Conclusions: 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.
Background: From June 22 through June 25, 2009, four outbreaks of infection with the pandemic influenza A (H1N1) virus occurred 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. Methods: All personnel with suspected infection were tested and clinically isolated if infection was confirmed. In addition, we 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. Results: 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 (95% credible interval, 1.50 to 2.36) before the intervention to 0.11 (95% credible interval, 0.05 to 0.20) 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. Conclusions: 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.
BACKGROUND: From June 22 through June 25, 2009, four outbreaks of infection with the pandemic influenza A (H1N1) virus occurred 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. METHODS: All personnel with suspected infection were tested and clinically isolated if infection was confirmed. In addition, we 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. RESULTS: 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 (95% credible interval, 1.50 to 2.36) before the intervention to 0.11 (95% credible interval, 0.05 to 0.20) 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. CONCLUSIONS: 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.
