Climatic drivers of melioidosis in Laos and Cambodia: a 16-year case series analysis

Creators: Bulterys, Philip L.; Bulterys, Michelle A.; Phommasone, Koukeo; Luangraj, Manophab; Mayxay, Mayfong; Kloprogge, Sabine; Miliya, Thyl; Vongsouvath, Manivanh; Newton, Paul N.; Phetsouvanh, Rattanaphone; French, Christopher T.; Miller, Jeff F.; Turner, Paul; Dance, David A. B.

Abstract

Background: Burkholderia pseudomallei is the cause of melioidosis, a serious and difficult to treat infection that is endemic throughout the tropics. Melioidosis incidence is highly seasonal. We aimed to identify the climatic drivers of infection and to shed light on modes of transmission and potential preventive strategies. Methods: We examined the records of patients diagnosed with melioidosis at the Microbiology Laboratory of Mahosot Hospital in Vientiane, Laos, between October, 1999, and August, 2015, and all patients with culture-confirmed melioidosis presenting to the Angkor Hospital for Children in Siem Reap, Cambodia, between February, 2009, and December, 2013. We also examined local temperature, humidity, precipitation, visibility, and wind data for the corresponding time periods. We estimated the B pseudomallei incubation period by examining profile likelihoods for hypothetical exposure-to-presentation delays. Findings: 870 patients were diagnosed with melioidosis in Laos and 173 patients were diagnosed with melioidosis in Cambodia during the study periods. Melioidosis cases were significantly associated with humidity (p<0·0001), low visibility (p<0·0001), and maximum wind speeds (p<0·0001) in Laos, and humidity (p=0·010), rainy days (p=0·015), and maximum wind speed (p=0·0070) in Cambodia. Compared with adults, children were at significantly higher odds of infection during highly humid months (odds ratio 2·79, 95% CI 1·83–4·26). Lung and disseminated infections were more common during windy months. The maximum likelihood estimate of the incubation period was 1 week (95% CI 0–2). Interpretation: The results of this study demonstrate a significant seasonal burden of melioidosis among adults and children in Laos and Cambodia. Our findings highlight the risks of infection during highly humid and windy conditions, and suggest a need for increased awareness among at-risk individuals, such as children.

Additional Information

© 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Open Access funded by Wellcome Trust. Available online 3 August 2018. This study formed part of the work programme of the MORU Tropical Health Network funded by the Wellcome Trust (grant number 106698/Z/14/Z). PLB received fellowship support from the National Institutes of Health National Institute of Allergy and Infectious Diseases (F30AI118342), the UCLA-Caltech Medical Scientist Training Program (T32GM008042), and the Paul and Daisy Soros Fellowships for New Americans. CTF and JFM were funded by the United States Department of Defense Joint Science and Technology Office and the Defense Threat Reduction Agency (projects HDTRA1-17-1-0015 and HDTRA1-11-1-0003). Funding sources played no role in study design or data interpretation. We thank all the physicians and nursing staff of the hospitals involved, the staff of the microbiology laboratories of Mahosot Hospital and Angkor Hospital for Children, and the Minister of Health and the Director of the Curative Department, Ministry of Health, Laos, for their support of this study. Contributors: KP, ML, MM, SK, TM, MV, PNN, RP, PT, and DABD oversaw clinical data collection. PLB and MAB oversaw climatic data collection. PLB, DABD, PT, PNN, JFM, and CTF conceived the study analysis. PLB and MAB did the analyses. PLB wrote the first draft of the paper. All study authors contributed to the review and drafting of the paper. We declare no competing interests.

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