Malaria outbreak investigation in Danchang District, Suphanburi Province, June 2023

Abstract

Background: On 26 June 2023, Division of Epidemiology (DoE), Department of Disease Control was notified from Suphanburi Provincial Health Office, of 11 malaria cases in non-transmission areas of Ongphra and Wangyao sub-districts, Danchang district. The joint investigation team comprising health personnel from DoE, Division of Vector Borne Diseases, Office of Disease Prevention and Control Region 5 Ratchaburi and Suphanburi Provincial Health Office investigated the outbreak during 27-30 June 2023 to confirm diagnosis and outbreak, describe epidemiological characteristics of outbreak, identify risk factors, and recommend preventive and control measures.

Methods: The investigation included review of malaria situation in Danchang district during 2018–June 2023, medical record review of malaria cases treated from December 2022 to June 2023, and active case finding in the affected villages. Laboratory examination of the cases were reviewed and an environmental investigation, including entomological survey in the villages were carried out.

Results: A total of 43 malaria cases were identified during December 2022 to June 2023. None died in this outbreak. Thirty-six cases received treatment from health care centers and 7 were found by active case finding. Of them, 42 were Thai (attack rate of 1.53/1,000 population) and the other one was Myanmar. Of the Thai cases, a higher malaria case rate was observed in males (1.78/1,000 population) than females (1.28/1,000 population). The outbreak affected all age groups. The highest malaria rate was found in Ongphra sub-district (5.02/1,000 population), followed by Wangyao sub-district (1.94/1,000 population). The first 3 malaria cases had onset in December 2022 and might be infected during their farming in malaria transmission areas of Kanchanaburi province. Subsequent cases were indigenous malaria in the villages in Danchang district, where there were main vectors of malaria (Anopheles maculatus and Anopheles minimus) by entomological survey. Delay in outbreak detection and response was noticed. All the cases were caused by Pv and only 18.18% of them had complete 4 times of standard follow-up.

Discussions and Conclusion: This vivax malaria outbreak occurred in non-transmission areas in Danchang district. The first 3 cases might be infected from malaria transmission areas of Kanchanaburi province and then the disease might spread in the villages where there were main malaria vectors following delay in outbreak detection and response. Effective surveillance, preventive and control measures, and good follow-up system of the cases are important in these areas.