New Delhi, Nov. 21: Parts of Bihar that did not conduct a second mass immunisation campaign against Japanese encephalitis have an unusually high incidence of the life-threatening viral illness this year, medical experts have said.

Paediatricians and outbreak investigators based in Gorakhpur have observed what they say is a sharp contrast between the proportion of Japanese encephalitis among children with encephalitis from Gopalganj, Siwan and West Champaran and children from neighbouring districts of eastern UP.

Among some 350 children from Bihar with encephalitis brought to a medical college in Gorakhpur, about 13 per cent have Japanese encephalitis. But among more than 2,600 children from eastern UP with encephalitis, only about 7 per cent have Japanese encephalitis, said Milind Gore, a senior scientist at the National Institute of Virology laboratory in Gorakhpur.

Gore and others believe the lower incidence of Japanese encephalitis in eastern Uttar Pradesh relative to the adjoining districts in Bihar is the result of a campaign to deliver a Japanese encephalitis vaccine in UP last year.

The Union health ministry had introduced a Chinese-made vaccine against Japanese encephalitis in 2006 after a large Japanese encephalitis outbreak in 2005 that had killed about 1,500 children. During 2010, another vaccination campaign was conducted in 20 districts across eastern India, two in Assam and seven in UP.

A note circulated by the health ministry at the Group of Ministers meeting on Japanese encephalitis today said vaccination and improved patient management measures have resulted in a decrease in the mortality during 2011.

However, the health ministry figures show that the number of children with acute encephalitis has increased over the past three years — 3,839 in 2008, 4,482 in 2009, and 5,149 in 2010 and 5,326 until October 7 this year.

The health ministry told the GoM that while the incidence of JE has reduced, a “large part of the acute encephalitis is due to enteroviruses.” But sources involved in the outbreak investigations have said they are unable to determine the cause of a majority of the encephalitis.

“We find enteroviruses in about 10 per cent of the cerebrospinal fluid samples of encephalitis patients,” said Komal Prasad Kushwaha, professor of paediatrics at the Baba Raghav Das Medical College in Gorakhpur. “This points to a role for enteroviruses in the encephalitis.”

The health ministry has said that the proportion of children with encephalitis who test positive for Japanese encephalitis has dropped from 36 per cent in 2005 to 7 per cent in 2011, attributing this decline to the vaccination campaigns.

“But it is still unclear why non-Japanese encephalitis has emerged around the same time that Japanese encephalitis has declined,” said Gore. “This is a question that needs to be addressed.”

The health ministry is expected to strengthen and expand the Japanese encephalitis vaccination campaigns, help improve patient management capabilities in district hospitals, as well as intensify public health activities that would seek to reduce the risk of enterovirus and JE infections.

“Acute encephalitis syndrome is not only a medical problem, but a broader development and rehabilitation challenge,” the ministry said in a presentation.