Incidence of Japanese Encephalitis and Acute Encephalitis Syndrome Hospitalizations in the Medium-Endemic Region in Central India.

BACKGROUND: We estimated the incidence of Japanese encephalitis (JE) and acute encephalitis syndrome (AES) following routine immunization with the live-attenuated SA 14-14-2 JE vaccine. METHODS: We implemented enhanced surveillance of AES and JE hospitalizations in endemic districts in Maharashtra and Telangana States during 2015-2016 and 2018-2020. We estimated incidence and compared differences in the incidence of JE and AES between two states, and vaccinated and unvaccinated districts during two study periods. We also considered secondary data from public health services to understand long-term trends from 2007 to 2020. RESULTS: The annual AES incidence rate of 2.25 cases per 100,000 children in Maharashtra during 2018-2020 was significantly lower than 3.36 cases per 100,000 children during 2015-2016. The six JE-vaccinated districts in Maharashtra had significantly lower incidence rates during 2018-2020 (2.03, 95% CI 1.73-2.37) than in 2015-16 (3.26, 2.86-3.70). In addition, the incidence of both JE and AES in two unvaccinated districts was higher than in the vaccinated districts in Maharashtra. Telangana had a lower incidence of both JE and AES than Maharashtra. The AES incidence rate of 0.95 (0.77-1.17) during 2018-2020 in Telangana was significantly lower than 1.67 (1.41-1.97) during 2015-2016. CONCLUSIONS: The annual incidence rate of Japanese encephalitis was < 1 case per 100,000 children. It indicated accelerated control of Japanese encephalitis after routine immunization. However, the annual incidence of acute encephalitis syndrome was still > 1 case per 100,000 children. It highlights the need for improving surveillance and evaluating the impacts of vaccination.

Infectious causes of acute encephalitis syndrome hospitalizations in Central India, 2018-20.

BACKGROUND: We enhanced surveillance of hospitalizations of all ages for acute encephalitis syndrome (AES) along with infectious aetiologies, including the Japanese encephalitis virus (JEV). METHODS: From October 2018 to September 2020, we screened neurological patients for AES in all age groups in Maharashtra and Telangana States. AES cases were enrolled at study hospitals along with other referrals and sampled with cerebrospinal fluid, acute and convalescent sera. We tested specimens for non-viral aetiologies viz. leptospirosis, typhoid, scrub typhus, malaria and acute bacterial meningitis, along with viruses - JEV, Dengue virus (DENV), Chikungunya virus (CHIKV), Chandipura virus (CHPV) and Herpes simplex virus (HSV). RESULTS: Among 4977 neurological hospitalizations at three study site hospitals over two years period, 857 (17.2%) were AES. However, only 287 (33.5%) AES cases were eligible. Among 278 (96.9%) enrolled AES cases, infectious aetiologies were identified in 115 (41.4%) cases, including non-viral in 17 (6.1%) cases - leptospirosis (8), scrub-typhus (3) and typhoid (6); and viral in 98 (35.3%) cases - JEV (58, 20.9%), HSV (22, 7.9%), DENV (15, 5.4%) and CHPV (3, 1.1%). JEV confirmation was significantly higher in enrolled cases than referred cases (10.2%) (p < 0.05). However, the contribution of JEV in AES cases was similar in both children and adults. JE was reported year-round and from adjacent non-endemic districts. CONCLUSIONS: The Japanese encephalitis virus continues to be the leading cause of acute encephalitis syndrome in central India despite vaccination among children. Surveillance needs to be strengthened along with advanced diagnostic testing for assessing the impact of vaccination.

Childhood encephalitis hospitalizations associated with virus agents in medium-endemic states in India.

BACKGROUND: Japanese encephalitis (JE) is the leading cause of childhood acute encephalitis syndrome (AES) in India. We enhanced the AES surveillance in sentinel hospitals to determine trends and virus etiologies in central India. METHODS: The neurological hospitalizations among children ≤15 years were tracked by using the AES case definition implemented by the national program. Acute and convalescent sera along with cerebrospinal fluid (CSF) specimens were collected and tested at the strengthened site hospital laboratories for anti-JE, anti-Dengue and anti-Chikungunya virus by IgM ELISA; along with Chandipura virus RT-PCR. Herpes simplex and enterovirus testing was undertaken at the reference laboratory. RESULTS: Among 1619 pediatric neurological hospitalizations reported during 2015-16, AES case definition was fulfilled in 332 (20.5%) cases. After excluding 52 non-AES cases, 280 AES cases resident from study districts were considered eligible for study. The treating physicians diagnosed non-viral causes in 90 cases, therefore 190 (67.9%) of 280 AES cases were suspected with viral etiologies. We enrolled 140 (73.7%) of 190 eligible AES cases. Viral etiologies were confirmed in 31 (22.1%) of 140 enrolled AES cases. JE (n = 22) was the leading cause. Additional non-JE viral agents included Chikungunya (5), Dengue (2) and Chandipura (2). However, only 21 (9.4%) of 222 additional AES cases referred from peripheral hospitals were confirmed as JE. CONCLUSIONS: Japanese encephalitis virus continues to be the leading cause of childhood acute encephalitis syndrome in central India despite vaccination program. Surveillance needs to be intensified for assessing the true disease burden of Japanese encephalitis following vaccination program implementation.