By Ram Dutt Tripathi BBC News, Lucknow

The first outbreak of encephalitis in Uttar Pradesh was recorded in 1978

More than 300 people have so far died of the disease and nearly 400 others have been admitted to various government hospitals.

The disease has spread to several districts along the Nepal border and in northern Bihar state.

The affected areas include several Buddhist pilgrimage sites.

One of the five worst affected districts is Kushinagar in Uttar Pradesh, where at least 54 people have died.

Thousands of foreigners arrive in Kushinagar from Nepal via Sonauli.

Many of them come only for a short period but some stay in Kushinagar for a month or longer.

Prolonged contact

Professor KP Kushwaha of Gorakhpur Medical College said all tourists who plan to stay for more than 15 days in an affected area should seek vaccination before they arrive.

He said the infection was caused only after prolonged contact with mosquitoes.

Dr T N Dhole of the Sanjay Gandhi Post Graduate Medical Institute in Lucknow called on embassies to issue health advisories to foreign tourists.

The main tourist season for Buddhist pilgrims starts in October, but some from Sri Lanka, China, Thailand and Japan have already arrived in region.