Japanese Encephalitis is a disease of Public Health importance because of it's epidemic potential and high Case Fatality Rate. It is mosquito borne zoonotic disease. It is primarily the disease of rural agricultural areas where mosquitoes proliferate in close association with pigs & other animal reservoirs. It's epidemic have also been reported in peri-urban & urban areas where similar conditions may exists.
JE in world
The virus infection is known to occur in Eastern Siberia, China, Japan, all of East Asia, Guam, Nepal & India. JE was described clinically in 1871 in Japan. It was formerly called Japanese B Encephalitis to distinguish it from Economo or type A encephalitis. The JE virus was isolated in 1935 from brain of fatal encephalitis cases and mosquito transmission was demonstrated in 1938. Since late 1960s, JE has virtually disappeared in Japan (,20 cases annually) and is declining in China (<10,000 cases annually). However, it remains a major problem in northern Thailand ( attack rates of 10 to 20 per 100,000 annually). In temperate climates, epidemics occur mostly in post monsoon months.
JE now occurs mainly in India, Nepal, China, Thialand & Vietnam and sporadicaaly in Indonaesia, Singapore & Malaysia. In endemic areas, children between ages 2 & 15 primarily affected. In non endemic areas all the age groups are affected, children & older adults being the predominant victims.
JE in India
In india, the disease was first reported in the mid 1950's from vellore in Tamil Nadu State, where cases of an encephalitis like illness were seen and serologically proven to be due to je or closely related to it. over the next decade, 52 cases of encephalitis presenting at the Christian Medical College, Vellore were identified to be JE. Around the same time, extensive serological surveys in South India revealed widespread flavivrus activity.
The first major epidemic of JE from India was reported from the Bankura and Burdwan districts of West Bengal in 1973. Since then, repeated annual outbreaks have occurred especially in the post monsoon, high mosquito season in West Bengal, Bihar, Aasam and the North East, Uttat Pradesh and the 3 southern states of Tamil Nadu, Karnataka & Andhra Pradesh. Sporadic cases are reported in the i nter epidemic periods also.
The first JE epidemic in the West Coast was reported from Goa in 1993. An outbreak of JE was reported from HAryana in 1990 and the disease was also seen in Orissa. Kerala Experienced the first epidemic in 1996. Thus it is clear that the disease is highly prevalent in southern and eastern parts of the country and it is also making inroads into newer areas. So far, epidemics are occurring in alternate years.
JE in Maharashtra
Till 2001, there was no problem of JE in Maharashtra State. But during 2002 & 2003 J. E. infection was introduced in eastern districts such as Bhandara, Gondiya, & Nagpur of Maharashtra State, where there was a focal outbreaks leading to 16 & 115 deaths respectively. During 2004 there were only 3 focal outbreaks of JE in districts Gadchiroli, Parbhani & Wardha & during 2005, there were 6 focal outbreaks of JE in Amravati, Yeotmal & Nagpur districts, leading no deaths occurred due to JE.
During June to August 2003, an outbreaks not confirmed as JE, reported from various parts of Nagpur division in Maharashtra. Similar outbreaks were reported from other states like A.P., Gujarath, Bihar also. The disease was labled as nagpur fever, Reye's syndrome, unusual measles etc. without proper verification of the etiological agent.
Total 393 Encephalitis cases with 115 deaths were reported during June to August 2003, from 15 districts of Maharashtra. Clinical samples of 202 cases were sent to NIV, Pune. All cases were in pediatric age group below 15 years age. There was no clustering and Usually a single case in villages was recorded.