Impact of flooding events on waterborne and vector-borne infections: a systematic review.

backgroundFlooding from natural disasters has become increasingly common worldwide, increasing the risk of infectious disease transmission, particularly waterborne and vector-borne infections. Although many studies report outbreaks following floods, the evidence remains fragmented across regions and pathogens. A comprehensive review is needed to clarify these associations and inform effective prevention and response strategies.

methodsA systematic search of PubMed, Embase, and the Cochrane Library was conducted between November 2024 and January 2025, identifying studies published from January 1, 2014, to December 31, 2024. Eligible studies assessed the association between flooding and waterborne or vector-borne infections and their health outcomes or evaluated related prevention and response interventions. Data were synthesized narratively due to study heterogeneity.

resultsOf the 1,785 records identified, 71 studies met the inclusion criteria. Flooding was consistently associated with increased incidence of waterborne infections, including leptospirosis, cholera, bacillary dysentery, and hepatitis A/E, as well as vector-borne infections such as dengue and malaria. Outbreaks varied by region, flood characteristics, and the strength of existing public health infrastructure. The lag period between the onset of flooding and disease emergence ranged from days to weeks. Timely interventions such as chemoprophylaxis, vaccination, water, sanitation, and hygiene (WASH) measures, and vector control may help mitigate outbreaks; however, most included studies were observational in design, and the overall certainty of evidence was low to moderate. Data on health system impacts, including hospitalization rates, intensive care unit burden, and mortality stratified by level of care, remain limited.

conclusionFlooding was most frequently associated with increased incidence of cholera, bacillary dysentery, leptospirosis, dengue, and malaria, each with distinct lag periods critical for outbreak prediction. Reported lag periods ranged from days to weeks. Limited observational evidence suggests that doxycycline chemoprophylaxis for leptospirosis, oral cholera vaccination, and early vector control may be useful in selected post-flood settings. These findings support strengthened post-flood surveillance and context-specific preparedness measures, while highlighting the need for higher-quality comparative studies. REGISTRATION: PROSPERO CRD42025635687. CLINICAL TRIAL NUMBE: Not applicable.