Epidemic and pandemic influenza in tropical Singapore : impact and effectiveness of response strategies
Creators: name: Lee, Vernon
Publisher: name: The Australian National University
Year: 2011
Subjects: subject: RA650.7.S55 L44 2011
subject: Influenza PreventionSingapore
subject: Epidemics PreventionSingapore
subject: Public health surveillance Singapore

description: Influenza is a disease of global significance, including in tropical regions where it spreads throughout the year. Understanding the spread and impact of influenza in the tropics is therefore important for preparedness planning. While there are numerous pharmaceutical and public health measures that attempt to reduce the spread and impact of influenza, few conclusive epidemiological studies are available to document their effectiveness. Scientific evidence is especially lacking for pandemic preparedness and response measures due to the rarity of pandemics. Singapore, a globally-connected, tropical Asian city-state, provides an excellent platform to determine the spread and impact of influenza in the tropics, and the effectiveness of public health measures in reducing the impact. This thesis aims to detail the impact of epidemic and pandemic influenza in Singapore, and to assess the effectiveness of various assessment and response measures in Singapore during the 2009 H1N1 influenza pandemic. Results: Influenza epidemics and pandemics were the likely cause of most excess mortality periods in Singapore from 1950 to 2000. Good surveillance is therefore important to detect epidemics for appropriate response. During the 2009 H1N1 influenza epidemic in Singapore, different methods for estimating influenza infection rates provided comparable findings if accurate input parameters were used. There are advantages and disadvantages to each method, and multiple methods should be used where possible for cross validation. One such method, a seroepidemiology cohort study, showed a 13% seroconversion rate in adults in the community and lower rates among hospital workers, suggesting that most of the population remained susceptible and required further protection. A surveillance program in the Singapore military during the peri-pandemic period showed the different clinical presentation of influenza compared to non-influenza cases, and introduced a clinical diagnostic model to help predict influenza among febrile respiratory illness cases for management. The possible effectiveness of combination strategies in reducing the impact of influenza was shown via a systematic review of mathematical modeling studies. It provides new evidence for the effectiveness of different strategies to reduce the spread of influenza in the military setting. One study showed that influenza vaccination may confer cross protection to other H1N1 strains, and previous exposure to pre-1957 H1N1 strains may confer some protection against the 2009 H1N1 strain. Another study showed the effectiveness of post-exposure ring prophylaxis with oseltamivir, together with prompt outbreak detection and isolation, as a containment strategy to reduce influenza spread. In the same setting, cessation of post-exposure prophylaxis did not result in subsequent disproportionate increase in infection rates, and asymptomatic infections occurred which may confer additional protection against future infection. While prophylaxis failures occurred, none were due to mutations that conferred resistance. Another study documented that public health measures such as enhanced surveillance with isolation, segregation and social distancing, and wearing personal protective equipment limited transmission of influenza.