According to the health ministry, till Aug 16, nine states reported 837 cases of the disease commonly known as brain fever. Deaths were reported from four states.
Uttar Pradesh reported 383 cases, Assam 368, Goa 44, Tamil Nadu 17, Manipur 11, Karnataka and Haryana six each. Kerala and Andhra Pradesh reported one case each.
Among the patients was a Nepalese national who was diagnosed with Japanese encephalitis at the Gorakhpur Medical College of Uttar Pradesh, close to the Nepal border.
Japanese encephalitis can affect the central nervous system and cause severe complications like paralysis, coma and finally death.
According to the World Health Organisation, the disease is fatal in up to 30 percent cases and there is a possibility that those who survive may be disabled for life.
UN officials say India can do much more to battle the disease.
Said Marzio Babille, chief of health wing at the UNICEF office here: "India produces only a tenth of the vaccine doses required for the country. India has good expertise to produce desired vaccines but they need to prioritise them.
"A good national immunisation plan, adequate doses of vaccine, ability of the government to investigate thoroughly and carry out surveillance are a few things required to handle the disease," Babille told IANS.
He said though mosquito was the primary reason for Japanese encephalitis, yet horses and pigs were the reservoirs of its virus.
"Many rural people in Gorakhpur are living in close proximity to pigs, and this could be one of the reasons why many cases are reported from this district of Uttar Pradesh," the official said.
He added that lack of consistent focus in the immunisation drive in Assam was a key reason for the high mortality in the state.
Of the 185 deaths, the highest toll was in Assam (115) and Uttar Pradesh was next with 65. While three people died in Haryana, two succumbed to the fever in Manipur.
Babille, however, said that the number of deaths across India had gone down and efforts must now be made to reach "zero mortality level".
A health ministry official said the main bottleneck in tackling the disease was a "cocktail of lack of awareness among our rural population and vaccine".
He said the most affected state of Uttar Pradesh had established a regional office of the health and family welfare department at Gorakhpur with support from the central government.
"The aim is to strengthen epidemiological and entomological surveillance in the eastern belt of Uttar Pradesh," he said.
Authorities said they have extended the Japanese encephalitis vaccination programme from 11 districts across four states in 2006 to 29 endemic districts across nine states.