An outbreak investigation of HFMD caused by Enterovirus 71 in a childcare center, San Pa Tong District, Chiang Mai, Thailand, 1-2 September 2015

Abstract

Background: On 1 September 2015, the surveillance and rapid response team was notified a cluster of Hand Foot and Mouth Disease (HFMD) in a childcare center. We started outbreak investigation with aimed to confirm the diagnosis, to confirm the outbreak, to describe the epidemiological characteristics, to identify the causative agent and to implement control and prevention measures in the childcare center.
Methods: Descriptive epidemiological study was conducted by active case finding in the center. Two case definitions were used. HFMD was a child who had rash or vesicle or pustule or scale in both hands and feet with oral ulcer. Herpangina was a child who had only oral ulcer in the throat. Environment and activity was also surveyed in the center. Risk factor was identified by retrospective cohort study and multivariate analysis by stratify analysis.
Results: Total 14 cases were met definitions in the center. Thirteen HFMD and one herpangina were identified. Overall attack rate was 26.92%. Male : female ratio was 1.33 : 1. Median age was 1 year old (range 1–4 years old). The onset was during 23-31 August 2015. Enterovirus 71 was identified (11/15 cases) and subsequent genogroup B5. Risk factors by univariate analysis was swallowing toy (RR = 3.00, 95%CI = 1.32-6.80) and playing with the case ( RR = 3.00, 95%CI 1.40-6.43) . Multivariate analysis by stratify analysis revealed swallowing toy ( adj. RR = 2.40, 95%CI 1.16-4.96) was a strongest risk factor. The center was closed for 7 days and disinfected with chlorine in the classroom and toys. Teachers did screening the ill child at the center entrance of the center for 7 days. After follow up for 14 days, there was no additional case.
Conclusions and discussions: HFMD and Herpangina outbreak caused by Enterovirus 71 was in the daycare center. The virus genotype B5 was frequently reported a severity such as encephalitis and fatal. Thus the rapid containment with disinfected by chlorine was crucial for prevent spreading and fatal outcome. The clinicians at San Pa Tong Hospital also be notified a high serious strain present in the area.