"In fact the disease remains a mysterious one," Additional Secretary (Health) R.P. Ojha said.

Manoj Paswan and his wife Lakhni Devi have lost all hope, as their three-and-a-half-year-old child is fighting for life after contracting AES. They are not paying heed to doctors' assurances that their child will survive. Both are praying for divine blessings for the recovery of their child.

Last week, they had admitted their only son in the encephalitis ward of the Sri Krishna Memorial College and Hospital in Muzaffarpur, but his condition has not shown any signs of improvement till date.

"We are praying to god to save our child now," Paswan, a landless farmer in his early 30s, told IANS.

Sunil Kumar, another parent of an AES-affected girl, said his daughter is in a critical condition. "Only the rain god can save my child as doctors told us that the monsoon will help to suppress the virus causing the disease," Kumar said.

In Muzaffarpur, worst affected by AES, the parents of AES-affected children have begun fearing the worst.

"We are helpless, hoping against hope for our child's survival," said Ranju Devi, mother of a five-year-old boy who has been at the Kejriwal hospital in Muzaffarpur for five days.

"Only god can save him now, we are praying for rains," Ranju, who belongs to the Musahar caste, a rat-eating community, that breeds pigs for a living and lives in abject poverty, told IANS.

Muzaffarpur civil surgeon Gyan Bhusan said that experts are of the view that monsoon rains will not only help bring down cases of AES but also help to treat children. "Heat wave conditions help the virus to spread and intensify the disease," he said.

Alarmed by rising numbers of children dying of AES in Muzaffarpur, a central team of experts from New Delhi-based National Centre for Disease Control visiting the district and decided to send samples collected from affected villages and a case study to an Atlanta-based virology lab to identify the cause of the deaths, health officials said.

The toll from the disease now stands at 236 with nearly 600 affected.

Most of the deaths were at the Sri Krishna Memorial College and Hospital and the Kejriwal Charitable Hospital. The worst affected districts include Patna, Gaya, Muzaffarpur, Sitamarhi, East Champaran and Vaishali.

Last year encephalitis had claimed 93 children in Gaya and 55 in Muzaffarpur.