Investigations Into the Outbreak of Chandipura Virus Encephalitis, Gujarat, India, 2024

Chandipura virus, a Vesiculovirus, was first identified in India during an outbreak investigation of acute febrile illness in 1965. The virus first gained global attention after being implicated as the causative agent of an outbreak of acute viral encephalitis characterized by rapid clinical deterioration and death, in 2003. Since then, the virus has caused multiple outbreaks in central and western Indian states. During July 2024, an increased incidence of acute encephalitis was reported from Gujarat state. In response an outbreak investigation was carried out and Chandipura virus was identified as the major etiology, accounting for 23.45% of the cases. Clinically, the disease was characterized by rapid progression of illness, with total duration of illness ranging from 24 to 72 h in majority of the cases. Vomiting was found to be significantly more in cases of Chandipura viral encephalitis. In the current outbreak, multiorgan dysfunction was identified as a complication in Chandipura infections. Serum glutamic-pyruvic transaminase and creatinine were found to be significantly elevated in cases of Chandipura encephalitis, compared to other etiologies of acute viral encephalitis. The case fatality rate in the current outbreak was 47.36%. Among the samples collected during the investigations, 69% humans and 8.76% animal samples tested positive for neutralizing antibodies against Chandipura virus. Fever surveillance during the outbreak also identified Chandipura IgM positive cases without neurological involvement, raising the possibility of Chandipura febrile illness. Phylogenetic analysis of the isolate from 2024 indicates similarity with isolates obtained during 2012 and 2014 from Gujarat.