|Description of measures of influenza-related illness during initial epidemic of pdmH1N1|
|Measure||Description||Period analyzed||No. at-risk/samples tested||No. of episodes/positive tests|
|GP-ILI: No. of ILIs per GP doctor||Based on ILI reporting by network of 23 GPs, where numerator is number of ILI reports and denominator is number of GPs reporting per day (median 14/d, IQR: 10-15); ILI is defined here as a consult for acute respiratory illness with a temperature of 38°C and above||25 Jun 2009 to 10 Oct 2009 (weeks 25 to 40)1||NA||NA||440||279|
|Lab-ILI: Proportion of ILIs at GP clinics testing positive for pdmH1N1||Based on testing of ILI samples from a separate sentinel GP network by the National Public Health Laboratory, where numerator is number of samples positive for pdmH1N1 and denominator is number of samples tested; ILI is defined here as a consult for acute respiratory illness with a temperature of 38°C and above||21 Jun 2009 to 10 Oct 2009 (weeks 25 to 40)2||1,372||1,029||878||656|
|Sch-LCC: Lab confirmed cases of pdmH1N1||Notifications of laboratory confirmed cases of pdmH1N1 as compiled by the Ministry of Education||12 Jun 2009 to 7 Oct 2009 (weeks 23 to 40)||270,3443||215,3793||654||533|
|Sch-DTM: Daily tempe-rature moni-toring||Temperature taking of students conducted twice daily in all schools; counts of the number of students detected to have fever on twice daily temperature taking is presented, with fever defined as 37.9°C and above for children of ages 12 years and below and 37.6°C and above for children of ages 13 years and above||30 Jun 2009 to 24 Jul 2009 (weeks 26 to 29)4||270,3443||215,3793||4,656||2,932|
|Sch-FRI: Febrile respiratory illness reporting||3 primary and 3 secondary schools from different areas of Singapore were selected to report FRI episodes, with FRI defined as fever of ≥ 37.5°C accompanied by either cough or sore throat; data was collated by the class teacher-in-charge once every 2 weeks||29 Jun 2009 to 3 Oct 2009 (weeks 26 to 39)5||4,320||4,821||964||1,178|
|Pre-SS and Post-SS: Pre-epidemic and post-epidemic serological surveys||Age-stratified serological data based on the proportion with hemagglutination inhibition titers ≥ 40 to pdmH1N1 in post-epidemic samples (Post-SS) minus that in pre-epidemic samples (Pre-SS), adjusted for the sensitivity of detecting confirmed infections using cross-sectional hemagglutination inhibition titers ≥ 40 to pdmH1N1||Pre-SS: 1 Feb 2008 to 31 May 2009||381||321||3||34|
|Post-SS: 1 Oct 2009 to 2 Jun 2010||124||96||41||39|
1 Estimates for epidemiological week 25 were extrapolated from the ILI rate for the 3 days (25 June to 27 June 2009) where data was available.
2 Only data from these dates were extracted, though surveillance extends before and after these dates.
3 Based on school enrolment on 29 June 2009.
4 Data on 29 June 2009 discarded due to inaccuracies in reporting on first day of school.
5 Up to week 34 for all 6 schools, and up to week 39 for 2 primary and 2 secondary schools.
Soh et al.
Soh et al. BMC Infectious Diseases 2012 12:336 doi:10.1186/1471-2334-12-336