Early detection for cases of enterovirus- and influenza-like illness through a newly established school-based syndromic surveillance system in Taipei, January 2010 ~ August 2011

Abstract

School children may transmit pathogens with cluster cases occurring on campuses and in families. In response to the 2009 influenza A (H1N1) pandemic, Taipei City Government officials developed a School-based Infectious Disease Syndromic Surveillance System (SID-SSS). Teachers and nurses from preschools to universities in all 12 districts within Taipei are required to daily report cases of symptomatic children or sick leave requests through the SID-SSS. The pre-diagnosis at schools is submitted firstly as common pediatric disease syndrome-groups and re-submitted after confirmation by physicians. We retrieved these data from January 2010 to August 2011 for spatio-temporal analysis and evaluated the temporal trends with cases obtained from both the Emergency Department-based Syndromic Surveillance System (ED-SSS) and the Longitudinal Health Insurance Database 2005 (LHID2005). Through the SID-SSS, enterovirus-like illness (EVI) and influenza-like illness (ILI) were the two most reported syndrome groups (77.6% and 15.8% among a total of 19,334 cases, respectively). The pre-diagnosis judgments made by school teachers and nurses showed high consistency with physicians' clinical diagnoses for EVI (97.8%) and ILI (98.9%). Most importantly, the SID-SSS had better timeliness with earlier peaks of EVI and ILI than those in the ED-SSS. Furthermore, both of the syndrome groups in these two surveillance systems had the best correlation reaching 0.98 and 0.95, respectively (p<0.01). Spatio-temporal analysis observed the patterns of EVI and ILI both diffuse from the northern suburban districts to central Taipei, with ILI spreading faster. This novel system can identify early suspected cases of two important pediatric infections occurring at schools, and clusters from schools/families. It was also cost-effective (95.5% of the operation cost reduced and 59.7% processing time saved). The timely surveillance of mild EVI and ILI cases integrated with spatial analysis may help public health decision-makers with where to target for enhancing surveillance and prevention measures to minimize severe cases.

Fig 1. The past (A) and current (B) syndromic surveillance systems of infectious diseases used in Taipei schools and other educational institutions.

(A) Traditional paper-based infectious disease reporting system through Fax submission (till 31 December, 2009) (B) Newly developed School-based Infectious Disease Syndromic Surveillance System (SID-SSS) starting from 1 January, 2010. Taipei CDC: Centers for Disease Control in Taipei.

Fig 2. Spatial diffusion of EVI (A) and ILI (B) syndromic cases in the Central Businesses District (CBD) and sub-urban areas of Taipei, at 10 week-peak periods of the epidemic seasons during the study period.

(A) EVI diffusion map with mean incidence from Week 19, 2010 to Week 28, 2010 (B) ILI diffusion map with mean incidence from Week 47, 2010 to Week 4, 2011 The four geographic groups A: Taipei Central Businesses District (Taipei-CBD), B: the para-CBD, C: the northern suburbs, and D: the south-eastern suburbs.

Fig 3. Temporal trends of EVI (A) and ILI (B) cases obtained from the SID-SSS were compared with those collected from the ED-SSS in Taipei City, 1 January, 2010 to 31 August, 2011.

SID-SSS: School-based Infectious Disease Syndromic Surveillance System ED-SSS: Emergency Department-based Syndromic Surveillance System “*” with light purple background indicates the winter vacation (Lunar New Year): Week 4–7, 2010 and 2011. “**” with light pink background indicates the summer vacation: Week 27–34, 2010. Our compiled and summarized data for Fig 3 are freely available in supplementary file in S2 Table.

Fig 4. Temporal trends in the incidence rates of EVI (A) and ILI (B) cases among the three age groups in the SID-SSS compared with those collected from the LHID2005 in Taipei City, 1 January 2010 to 31 August 2011.

SID-SSS: School-based Infectious Disease Syndromic Surveillance System LHID2005: Longitudinal Health Insurance Database 2005 “*” with light purple background indicates the winter vacation (Lunar New Year): Week 4–7, 2010 and 2011. “**” with light pink background indicates the summer vacation: Week 27–34, 2010.