Imported malaria in South-west Delhi: Five-year epidemiological trends (2020–2024) from a fever clinic and implications for urban malaria elimination

BACKGROUND OBJECTIVES: Urban malaria remains a significant public health challenge, driven by population mobility, and complex transmission dynamics. To characterize the epidemiological profile of malaria cases, with emphasis on demographic patterns, parasite species distribution, and contribution of imported malaria in South-west Delhi. METHODS: The clinical records from the Fever Clinic at ICMR-National Institute of Malaria Research, New Delhi were analysed. Febrile patients were screened for malaria using rapid diagnostic tests and microscopic examination of peripheral blood smears. Data on age, gender, parasite species, stage and travel history (past 30 days) to malariaendemic areas were extracted. Cases were classified as imported or indigenous based on established epidemiological criteria. RESULTS: Among 7257 fever cases, 58 (0.8%) were tested malaria positive. Plasmodium vivax accounted for 94.8% (55/58) of cases and P. falciparum for 3.4% (2/58). Males (70.7%) and individuals aged 18-45 yrs (60.3%) were most affected. Imported cases accounted for 51.7% (30/58), with 76.7% (23/30) from Aligarh, Amorha, Budaun, Bulandshahr, Hardoi and Shahjahanpur districts. The proportion of imported cases increased from 52.2% in 2020 to 66.7% in 2024, concurrent with a decline in indigenous malaria cases. INTERPRETATION CONCLUSION: Malaria persists in South-west Delhi, with low transmission, P. vivax predominance and substantial, increasing proportion of imported cases from neighbouring districts of Uttar Pradesh and other endemic areas. These findings highlight the critical need for strengthening cross-notification to State, case-based surveillance and inter-state collaboration, targeted vector control and pre-emptive interventions in both recipient area and districts from where population migrates to Delhi with malaria infection to sustain malaria elimination in urban India.