At least 74 children have died so far this year because of an outbreak of encephalitis in Odisha’s Malkangiri district, Hindustan Times reported on Thursday. All of those who have died belong to the tribal Koya community, state officials said. While 47 deaths were caused by Acute Encephalitis Syndrome, 27 were attributed to Japanese Encephalitis.

Joint Director of the National Vector-Borne Disease Control Programme in Odisha Dr MM Pradhan called the occurrence of the disease “the biggest outbreak in the district”. “We are studying why it is happening,” he said. Meanwhile, state director of health services Dr Chittaranjan Nayak said a vaccination programme in the district against Japanese Encephalitis would begin on December 1. “The process of procuring the vaccines from the Centre, training the staff and the logistical assessment has begun,” he said.

The disease has hit 18 villages across Malkangiri with the Kalimela, Mathili and Podia blocks worst affected. The first recorded incidence of Japanese encephalitis in Malkangiri district was in 2011. Between 2011 and 2014, 15 children have died of the disease but there were no fatalities in 2015.

The Japanese encephalitis virus is a flavivirus related to the dengue, yellow fever and West Nile viruses, and is spread by mosquitoes. The Japanese encephalitis virus is the main cause of viral encephalitis in many countries of Asia with an estimated 68,000 clinical cases every year. Health officials have so far struggled with efforts to remove carriers of the virus such as pigs from Malkangiri because of the population of the district using the animals as a source of food and income.