Influenza virus type A (subtypes H1N1, H2N2, H3N2), B and C. Influenza type C infection causes a febrile mild upper respiratory illness and does not occur in epidemics.
24 - 72 hours
One day before symptoms develop and up to 5-7 days after symptom onset.
Mainly via respiratory droplets and direct contact with nasal or throat secretions.
Influenza A and B virus infections occur all year round in Singapore with small peaks in the middle and the end/beginning of the year.
In April 2009, an outbreak of influenza caused by a novel influenza A virus (H1N1- 2009), was reported in Mexico. It subsequently spread to the rest of the world. Singapore reported its first case in a returning student from New York, US, on 26 May 2009. On 11 June, the World Health Organisation (WHO) declared the first influenza pandemic of the 21st century. By September 2009, it was estimated that at least 270,000 persons had been infected in Singapore. A total of 18 H1N1-related deaths were reported during this period, representing slightly more than 1% of hospitalized cases and a case fatality rate of 6.7 per 100,000 cases. The WHO declared an end to the pandemic in August 2010.