Surveillance for influenza requires internal and external monitoring for virus strains and disease activity. Early identification of circulating or novel strains through an integrated surveillance system is essential for pandemic detection and vaccine preparation.

Collaboration among the World Health Organisation (WHO) global influenza laboratory network leads to recommendations for annual vaccine production. Reference strains and seed viruses appropriate for manufacturing are developed and vaccines and diagnostic reagents prepared.

Existing Influenza Surveillance in Singapore

Ministry of Health (MOH) Communicable Diseases Surveillance Branch coordinates national influenza surveillance, which comprises five main components: community surveillance, laboratory surveillance, hospital surveillance, veterinary surveillance through the Agri-Food and Veterinary Authority (AVA), and external surveillance. This occurs throughout the year, as Singapore, unlike many countries, generally experiences influenza year-round with a bi-modal increase in influenza activity during two periods of the year.

MOH's current surveillance objective is to have in place an integrated surveillance system that is well prepared to detect first cases or unusual clusters of influenza in animals or humans, and to identify the emergence of a novel influenza virus in a timely manner.

1. Community Surveillance. Community-wide surveillance of acute respiratory infections (ARI) has been well established in Singapore. Weekly reports are compiled from the public-sector hospitals and polyclinics.
   
   
2. Laboratory Surveillance. Virological surveillance of influenza viruses is routinely carried out by the National Influenza Centre on respiratory samples from hospitals and polyclinics.
   
   
3. Hospital Surveillance. MOH has implemented a post-SARS epidemic surveillance system in all acute hospitals since August 2003. This ongoing surveillance system includes surveillance of atypical pneumonia, prolonged unexplained fever and sudden acute respiratory death. Hospitals continue to support the post-SARS epidemic surveillance system. Patients fulfilling the surveillance criteria are reported to MOH via the online Case Reporting Form (CRF) System. Early cases of influenza presenting with severe acute respiratory illness are likely to fulfil the same criteria.
   
   In addition, any unusual occurrence of infectious illness observed by hospitals are also reported to MOH, via the surveillance phone which is manned by Communicable Diseases Surveillance staff, twenty-four hours a day, seven days a week.
   
   
4. Veterinary Surveillance. The Agri-Food and Veterinary Authority (AVA) carries out surveillance on poultry, based on the assumption that poultry infection and deaths will precede human infection.
   
   
5. External surveillance. MOH performs continuous monitoring of infectious disease situations in the region and globally, via various sources, to identify external health risks and threats. Where incidents of concern emerge in a given country, clarification is sought directly through international contacts.