The profile of imported malaria in Sri Lanka from 2013 to 2023.

Sri Lanka was certified malaria-free by the World Health Organization in 2016 and has remained so since then. Yet, imported malaria cases and the presence of mosquito vectors in parts of the country threaten the re-establishment of malaria. Data on imported malaria cases diagnosed from 2013 to 2023 in Sri Lanka were extracted from the National Malaria Database containing detailed data on every case of malaria maintained at the Anti Malaria Campaign, Sri Lanka. Descriptive analyses were carried out to characterize imported malaria in the country. A total of 532 imported malaria cases were reported during the study period, over half of them (68.5%) were those who traveled for employment as low-wage or high-wage workers. Infections with all four human malaria species were imported, with a majority being Plasmodium (P.) falciparum (48.1%), most acquired in Africa, and P. vivax (40.5%), most acquired in India. Imported P. ovale infections took longer to manifest clinically from time of travel (median 95 days) than did other Plasmodia infections (median 14 days). Infections with P. malariae took longer to diagnose from onset of illness (median 15.5 days) than other Plasmodium species (median 4-6 days). Patients accessed healthcare for their malaria illness sooner (geometric mean = 2.42 days) than physicians took to diagnose malaria (geometric mean 3.41 days) (p < 0.001). Seven patients with P. falciparum recrudesced and three with P. vivax relapsed. Forty-six imported malaria cases were severe, all but one due to P. falciparum, and one death occurred among them over the study period. Epidemiological features of imported malaria were species-specific and related to the biology of the Plasmodium species. A large proportion of imported malaria, predominantly P. falciparum and P. vivax, was associated with work-related travel. The parasite species incidence over the years followed trends of incidence reported from Africa and India from where they were predominantly imported. The delay in diagnosing imported malaria which increases the risk of morbidity and mortality, and also risks the re-establishment of malaria in the country were mainly on the part of the physicians and not due to patients delaying seeking treatment.