tetano
Editor, Senior Moderator
Editorial
Volume 362:2221-2223 June 10, 2010 Number 23
2009 H1N1 Virus Transmission and Outbreaks
Timothy M. Uyeki, M.D., M.P.H., M.P.P.
The emergence of 2009 pandemic influenza A (H1N1) virus prompted early questions about how the virus was spreading and how easily it was transmitted, along with uncertainty about disease severity, clinical complications and risk factors for severe disease, and the effectiveness of antiviral treatment and control measures. Without a vaccine against the 2009 H1N1 virus, early control measures included both pharmaceutical interventions (the use of antiviral agents) and nonpharmaceutical interventions (e.g., school closures, isolation, and quarantine), depending on the specific outbreak setting, available resources, and goals. The use of these interventions varied according to country and the evolution of the pandemic. It was determined quickly that the 2009 H1N1 virus was resistant to the adamantane antiviral agents but susceptible to neuraminidase inhibitors (oseltamivir and zanamivir),1 which could be used for treatment and chemoprophylaxis.2
In this issue of the Journal, findings of two studies that were conducted during the early phase of the pandemic are reported, with implications for the control of influenza outbreaks. Lee and colleagues3 report efforts to control outbreaks of 2009 H1N1 virus infection among military personnel in Singapore. Oseltamivir chemoprophylaxis and other interventions (isolation and oseltamivir treatment of confirmed cases, active surveillance for influenza-like illness among persons receiving oseltamivir chemoprophylaxis, and home quarantine of close military contacts of index cases) were implemented together in four separate outbreaks. Three outbreaks occurred among military personnel who lived in barracks during weekdays and at home on weekends, and one was among health care workers at a military medical center. In this study, "ring prophylaxis" was used, meaning that oseltamivir chemoprophylaxis was used more widely than just among close contacts. In three of the four outbreaks and for the pooled overall data, the number of cases of 2009 H1N1 virus infection among military personnel decreased significantly after the interventions were implemented. In one outbreak in which all personnel were administered oseltamivir chemoprophylaxis and quarantined at home, the investigators concluded that the use of oseltamivir accounted for the sharp drop in the number of symptomatic cases.
....
Controlling outbreaks among young military personnel with high adherence to oseltamivir chemoprophylaxis may not reflect the experiences in other settings, including those involving high-risk patients (e.g., elderly residents in long-term care and severely immunosuppressed patients in a hospital setting7,8). For example, compliance with oseltamivir chemoprophylaxis by schoolchildren in the United Kingdom was reduced because of gastrointestinal symptoms.9 Although the emergence of oseltamivir-resistant 2009 H1N1 virus infection that is associated with a His275Tyr mutation in viral neuraminidase has been rare to date, sporadic cases have occurred worldwide, including among persons receiving oseltamivir chemoprophylaxis.8 Practitioners who are considering the use of oseltamivir chemoprophylaxis for the control of outbreaks need to weigh the potential for the development of oseltamivir resistance. Limited transmission of oseltamivir-resistant strains has occurred among both previously healthy persons and severely immunosuppressed patients.8 Thus, appropriate antiviral management (zanamivir if available), the use of strict infection-control measures to prevent further transmission,10,11 and antiviral-resistance testing are especially important when oseltamivir resistance is suspected.2 If widespread prevalence of oseltamivir resistance develops in circulating 2009 H1N1 virus strains, zanamivir will be the remaining approved antiviral option for treatment and chemoprophylaxis. However, the best way to control influenza outbreaks is to prevent them from occurring as much as possible, and influenza vaccination is the primary prevention tool.
http://content.nejm.org/cgi/content/full/362/23/2221
Volume 362:2221-2223 June 10, 2010 Number 23
2009 H1N1 Virus Transmission and Outbreaks
Timothy M. Uyeki, M.D., M.P.H., M.P.P.
The emergence of 2009 pandemic influenza A (H1N1) virus prompted early questions about how the virus was spreading and how easily it was transmitted, along with uncertainty about disease severity, clinical complications and risk factors for severe disease, and the effectiveness of antiviral treatment and control measures. Without a vaccine against the 2009 H1N1 virus, early control measures included both pharmaceutical interventions (the use of antiviral agents) and nonpharmaceutical interventions (e.g., school closures, isolation, and quarantine), depending on the specific outbreak setting, available resources, and goals. The use of these interventions varied according to country and the evolution of the pandemic. It was determined quickly that the 2009 H1N1 virus was resistant to the adamantane antiviral agents but susceptible to neuraminidase inhibitors (oseltamivir and zanamivir),1 which could be used for treatment and chemoprophylaxis.2
In this issue of the Journal, findings of two studies that were conducted during the early phase of the pandemic are reported, with implications for the control of influenza outbreaks. Lee and colleagues3 report efforts to control outbreaks of 2009 H1N1 virus infection among military personnel in Singapore. Oseltamivir chemoprophylaxis and other interventions (isolation and oseltamivir treatment of confirmed cases, active surveillance for influenza-like illness among persons receiving oseltamivir chemoprophylaxis, and home quarantine of close military contacts of index cases) were implemented together in four separate outbreaks. Three outbreaks occurred among military personnel who lived in barracks during weekdays and at home on weekends, and one was among health care workers at a military medical center. In this study, "ring prophylaxis" was used, meaning that oseltamivir chemoprophylaxis was used more widely than just among close contacts. In three of the four outbreaks and for the pooled overall data, the number of cases of 2009 H1N1 virus infection among military personnel decreased significantly after the interventions were implemented. In one outbreak in which all personnel were administered oseltamivir chemoprophylaxis and quarantined at home, the investigators concluded that the use of oseltamivir accounted for the sharp drop in the number of symptomatic cases.
....
Controlling outbreaks among young military personnel with high adherence to oseltamivir chemoprophylaxis may not reflect the experiences in other settings, including those involving high-risk patients (e.g., elderly residents in long-term care and severely immunosuppressed patients in a hospital setting7,8). For example, compliance with oseltamivir chemoprophylaxis by schoolchildren in the United Kingdom was reduced because of gastrointestinal symptoms.9 Although the emergence of oseltamivir-resistant 2009 H1N1 virus infection that is associated with a His275Tyr mutation in viral neuraminidase has been rare to date, sporadic cases have occurred worldwide, including among persons receiving oseltamivir chemoprophylaxis.8 Practitioners who are considering the use of oseltamivir chemoprophylaxis for the control of outbreaks need to weigh the potential for the development of oseltamivir resistance. Limited transmission of oseltamivir-resistant strains has occurred among both previously healthy persons and severely immunosuppressed patients.8 Thus, appropriate antiviral management (zanamivir if available), the use of strict infection-control measures to prevent further transmission,10,11 and antiviral-resistance testing are especially important when oseltamivir resistance is suspected.2 If widespread prevalence of oseltamivir resistance develops in circulating 2009 H1N1 virus strains, zanamivir will be the remaining approved antiviral option for treatment and chemoprophylaxis. However, the best way to control influenza outbreaks is to prevent them from occurring as much as possible, and influenza vaccination is the primary prevention tool.
http://content.nejm.org/cgi/content/full/362/23/2221