In Uttar Pradesh, since August 1, this form of epidemic brain fever transmitted by bites of infected mosquitoes has claimed at least 150 people, mostly children.
The authorities say measures such as anti-larval treatment, indoor spray and fogging have already been taken up in sensitive areas to eradicate the disease.
Besides, they say hospitals have been alerted and isolated wards set up for the treatment of such patients.
But the toll has been on a steady rise, with affected people from Nepal and Bihar also being admitted in hospitals in Uttar Pradesh.
Officials say there was no specific remedy for this fever and "only life-sustaining measures were being undertaken".
He said the blood serum samples of the patients were being sent to the National Institute of Infectious Diseases and to the Regional Laboratory, Lucknow, for examination.
The tests may take up to a month.
Pigs are the main carriers of the encephalitis virus, which is transmitted to humans through mosquito bites. The authorities have also advised people to use mosquito nets and to take other measures to destroy the parasites.
(Seen in picture is a man rushing his child to a hospital in Ghorakpur, Uttar Pradesh.)
Photograph: AP