To determine the contribution of Orientia tsutsugamushi, the agent of scrub typhus, as a cause of acute encephalitis syndrome (AES) in Assam, India, we conducted a retrospective study of hospital patients with symptoms of AES during 2013–2015. Our findings suggest that O. tsutsugamushi infection leads to AES and the resulting illness and death.

Our findings confirm wide circulation of rickettsial infections and their probable vectors in the northeast region of India.Accession numbers: KU163367, KU163368, KU499847, KU499848.

KU163366, KY594249, KY594248, KY594251, KU163359, KU163361, KU163363, KU163369, KY594250, KP067915, KU163373, KU163372, KU163370, KU163364, KU163362, KY594247, KY594252, KU163360, KU163365, KU163367, KU163368, KU163371, KX1555826, KY594257, KY594255, KY594256, KX155825, KX155829, KX155827, KX155828, KY594254, KY594253, KY594258, KY583503, KY583499, KY583501, KY583500, KY583502.

A cross-sectional survey was undertaken to estimate seroprevalence of immunoglobulin G antibodies against scrub typhus, spotted fever group rickettsiae, and typhus group rickettsiae in randomly selected 48 clusters in 12 districts of 3 Northeast states of India: Assam, Meghalaya, and Tripura. Individuals in 3 age groups (5-8, 9-17, and 18-45 years) were selected from each cluster. Sera (N = 2360) tested were collected as part of a national survey on dengue seroprevalence conducted between September 2017 and February 2018. Overall, seroprevalence of 2.5% was detected against rickettsioses, with highest positivity against spotted fever group rickettsiae, followed by scrub typhus and typhus group rickettsiae. Seroprevalence was highest in Tripura (3.7%), followed by Assam (2.6%) and Meghalaya (1.04%). Adults of 18 to 45 years of age were found to be most affected (3.8%). The study findings indicate the need for increasing testing facilities for active case detection at hospital levels. Efforts on implementing effective preventing strategies are suggested to be targeted in disease-specific endemic foci.