Epidemiological investigation of Chandipura virus disease outbreak, Gujarat, India, July 2024: a matched case-control study

Chandipura virus disease (CHPVD), caused by the sandfly-transmitted Chandipura virus, is a major public health concern due to its reported explosive outbreaks of Acute Encephalitis Syndrome (AES) and high mortality in children. We aimed to describe the clinico-epidemiological characteristics of the cases and identify risk factors, following laboratory confirmation of CHPVD in Gujarat, India, in July 2024. We defined case as laboratory-confirmed CHPVD in clinical presentation of AES in a child aged under 15 years from Gujarat in July 2024. We identified cases through enhanced passive surveillance and compared them to age and place-matched controls. We randomly selected two controls (same and neighbouring village) with no fever and seizures or altered sensorium in previous month and aged +/-two years from case-age. We collected data using structured questionnaire. Severe underweight was weight-for-age z-score < -3 Standard deviation. We calculated geometric-mean (GM) for laboratory investigations, adjusted OR (aOR) using conditional logistic regression with Firth penalization. We conducted an entomological survey for sandflies in and around case household. We identified 54 cases with median age of 4 years [Interquartile-range (IQR) = 2–7] and 59% males in 20/33 districts. Case fatality rate was 50%. Rural cases were 81%, 72% had domestic animals, and 34.8% were severely underweight. Clinical manifestations were fever (87%), convulsion (74%), vomiting (70.4%), altered sensorium (57.4%), and loose stools (48%). Median duration between symptom onset and hospital admission was 1 day (IQR:0–2), and from hospital admission to death was 3 days (IQR:2-5.75). WBC count (GM = 15295/mm 3 ), SGOT (GM = 121.7U/L), APTT (GM = 48.9 s) and Lactate dehydrogenase (GM=657U/L.) were elevated. CSF showed lymphocytic predominance, and protein was 63 mg/dL. Underweight status in child (aOR = 4, 95%CI = 1.4–14.3) and poor housing structures and conditions (aOR = 2.66, 95%CI = 1.71–4.93) were significant risk factors. We collected sandflies (Sergentomyia species) from dwelling units while insecticidal control measures were underway. This investigation highlights widespread nature and high mortality from CHPVD outbreak among children in Gujarat. Clinical findings were consistent with acute encephalopathy and disseminated systemic infection. Being underweight and poor housing conditions were risk factors. We recommended physician sensitization in case management, health communication to address nutrition, housing conditions and protection against the sandfly bites. Not applicable.