More than 20 million children across 60 districts in northern India, considered endemic to Japanese encephalitis, will be vaccinated against the mosquito-borne disease, the health minister said Monday.

An outbreak of the disease in the impoverished Uttar Pradesh state has killed nearly 650 people, mostly children, and more than 3,000 infected with the disease are being treated at hospitals across the state.

The disease has also killed at least 172 people in neighboring Nepal, which shares a long border with Uttar Pradesh.

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Although the disease, which mostly affects children, is preventable with vaccination, officials in Uttar Pradesh state say they lack the money to do it and have sought help from the federal government and the World Health Organisation.

Health Minister A Ramdoss said the federal government was ready to bear the cost of vaccination. He didn't specify any figure, but said the government has already sought global tenders for the vaccine.

Japanese encephalitis causes high fever and vomiting, and can sometimes lead to coma and death.

Children are most susceptible to the disease, and many of the dead in the outbreak have been under age 15.