Outbreak investigation of Zika virus infection in Klong khoi Subdistrict, Pak kret District, Nonthaburi, Thailand, April–May 2018

Abstract

Background: On 14th May 2018, Nonthaburi Provincial Public Health Office received the notification of 2 cases of Zika virus disease in Village 6, Klong khoi subdistrict, Pak Kret district, Nonthaburi. The Provincial Health team then conducted the outbreak investigation, set the surveillance and launched the prevention and control measures during 14 April–15 May 2018. The objectives were to confirm the diagnosis as well as the outbreak, to know the distribution of the outbreak and to recommend prevention and control measures.
Methods: The descriptive study was performed by interviewing the patients, reviewing the medical records, finding the active case in the community by using case definitions adapted from the Surveillance Guideline of Bureau of Epidemiology and collecting the urine of household contacts and a pregnant woman for laboratory testing. The environmental survey was conducted at the patient’s house and also in the community located within 100-metres radius around patient’s house.
Results: Totally, two Zika confirmed cases were found in this outbreak. Both cases live in the same home. No further patients were found from active case finding in the community. By the environmental survey, we found many wet areas as well as containers that could be Aedes mosquito breeding place. One week before the notification of cases, the larva index of 100 meter radius around patient’s house show high percentage. Household index (HI) and container index (CI) were 20% and 25.86%, respectively.
Discussions and conclusions: This Zika outbreak was limited only in Village 6, Klong khoi subdistrict, Pak kret district, Nonthaburi Province. This outbreak could be a new outbreak or the continuity from the last outbreak in February 2018. The important risk factors were ‘many Aedes mosquito bleeding site within and around patient’s house’, ‘Patients’ activities in daily life’ and ‘high intensity of Aedes mosquito’. For the prevention and control measures, we gave health education to the community, eliminated the mosquito breeding site, sprayed insecticide to control of Aedes mosquito, monitored larval index (HI and CI) and set the active surveillance system in the community. The results showed no further new Zika cases within 28 days and the outbreak was stopped.