Epidemiological and clinical characteristics of malaria patients in Khanh Hoa, Vietnam: the rise of Plasmodium malariae

Background: In Vietnam, an unusual rise in P. malariae cases has been observed, accounting for a high proportion of malaria infections in Khanh Hoa province. Objective: To describe the epidemiological and clinical characteristics of malaria cases caused by P. malariae in Khanh Hoa province, Vietnam, and to assess its recent emergence and distribution pattern. Methods: A cross-sectional study was conducted in Khanh Vinh region, Khanh Hoa province, Vietnam. Confirmed malaria cases were collected from medical and laboratory records, including demographic, clinical, and parasitological data. Analyses identified trends and patterns of P. malariae infection. Results: 93.68% of malaria infections were caused by P. malariae and 6.32% by P. vivax. Symptomatic P. malariae accounted for 96.63% of cases, with renal involvement (41.6%), splenomegaly (40.5%), and hepatomegaly (37.1%). The majority of infections occurred in the working-age population (64.2%). The Raglai ethnic group exhibited the highest prevalence (54.7%). The most affected occupation were farmer (72.6%) and students (18.9%). The highest infection rates were observed in Nam Khanh Vinh (36.8%) and Tay Khanh Vinh (37.9%), while P. vivax infections were reported solely in Bac Khanh Vinh and Nam Khanh Vinh. Conclusions: P. malariae was the predominant species, largely associated with symptomatic infection and frequent renal, splenic, and hepatic involvement. Infections mainly affected the working-age population, with higher prevalence among the Raglai ethnic group, particularly farmers and students, and showed an uneven spatial distribution, with the highest burden in Nam Khanh Vinh and Tay Khanh Vinh.