The diagnostic lens: on encephalitis

A paper in the Indian journal Current Science suggests an unexpected cause for the inflammatory brain disease — encephalitis — found in Malkangiri district of Odisha. For many years, this recurring outbreak, which killed over 100 children last year, was thought to be due to the Japanese encephalitis (JE) virus . Now researchers say it was likely due to the consumption of a wild bean, called Bada Chakunda, which grows freely in the region. Like several natural toxins, the anthraquinones in the bean don’t harm healthy people, but cause fatal dysfunction of the liver, heart and brain in underfed children. This finding draws on the researchers’ previous work in Uttar Pradesh’s Saharanpur district, where too a recurrent encephalitis outbreak was traced to this bean. While more data may be needed to confirm this link, it is clear the Malkangiri scourge wasn’t JE. This is only the latest in a series of such investigations in which suspected pockets of JE turned out to be something else. An illness around for three decades in U.P.’s Gorakhpur turned out, primarily, to be scrub typhus last year, while epidemics in Bihar’s Muzaffarpur were linked to lychee consumption, again among emaciated children. In all these cases, the suspicion of JE, though the epidemiology and symptoms didn’t match, delayed the discovery of the cause.


Why does this keep happening? One answer is that JE was indeed the biggest cause of encephalitis in India for decades, and today the public health diagnostic machinery is built around this illness. But as JE vaccination rates have grown, incidence has shrunk, and a host of other causes of encephalitis, like dengue, scrub typhus, herpes simplex and the West Nile virus, have emerged to the forefront. Yet, investigating agencies such as the National Centre for Disease Control and the National Institute of Virology have persisted in focussing on JE. Another problem is the archaic format in which encephalitis is reported to the government. This too is a relic of the pre-JE-vaccination era. Under this format, if an encephalitis case cannot be confirmed as JE, doctors tag it as Acute Encephalitis Syndrome (AES), a term that has now crept into medical literature. But AES is no diagnosis, just a temporary label for different unnamed diseases. Classifying them all under one head gives doctors the false sense of security of having pinpointed the illness, the researchers behind the Malkangiri finding argue. It is time for Indian investigators to update their understanding of encephalitis and look at outbreaks through a wider lens. If JE made 2,043 Indians sick this year, the mysterious AES is reported to have affected six times as many. A fixation with JE means the numerous patients in the second group may never get a diagnosis.

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Printable version | Sep 30, 2022 8:15:07 am | https://www.thehindu.com/opinion/editorial/the-diagnostic-lens-encephalitis/article59780890.ece