New Delhi, Sept. 21: The Union health ministry today labelled Japanese encephalitis a "notifiable disease", directing states to ensure that doctors inform local health officers about every case in efforts to improve estimates of this potentially lethal viral infection.

The notification - sent to all state health departments and the chief secretaries of selected states, including Bengal and Bihar, with high burdens of JE in recent years - will require doctors to inform district health officers about JE cases they encounter.

"It is essential to have complete information of all JE cases," the ministry said in its notification that requires doctors to report patients diagnosed as JE either through antibodies or isolation of virus from their bloodstream.

The health ministry has documented over 4,400 cases of JE and 786 JE-linked deaths between 2013 and 2015, most of the cases clustered in Assam, Bengal, Bihar and Uttar Pradesh. This year, until August 31, Bengal reported 91 cases and 18 deaths, while Bihar reported 43 cases and nine deaths.

While the JE virus is transmitted through mosquito bites, the diagnosis of the encephalitis has been challenging because of simultaneous outbreaks of what public health experts call acute encephalitis syndrome (AES) in these states.

The health ministry has documented over 27,000 AES cases over the past three years. Public health experts have in the past cautioned that poor surveillance, incomplete diagnosis and absence of notification are among factors that have stymied India's efforts to control JE and AES.

Health officials say early detection of JE is critical for effective implementation of measures, such as mosquito population control, to curb the spread of the infection and to manage JE patients. The infection, which involves the brain, can become life-threatening or leave survivors with long-term handicaps.

Under the notification issued today, all doctors, whether working in government or private hospitals, nursing homes, or clinics will need to inform district or municipal health officers if they detect a patient with JE.

Blood samples of all suspected JE patients would need to be sent to a sentinel surveillance hospital for confirmation. The JE cases will need to be managed under guidelines prescribed by the Union health ministry on the website of the National Vector Borne Disease Control Programme.

The health ministry's directive adds JE to the list of other notifiable diseases in India that include tuberculosis, dengue, measles, diphtheria and tetanus, among others.

The Union health ministry initiated mass vaccination campaigns in the affected states in eastern India in 2006, but thousands of children in the states have become ill during repeated outbreaks of JE and the mystery-encephalitis called acute encephalitis syndrome.