Acute encephalitis is widely prevalent in India and its sub-continent. They cause
great burden on morbidity and mortality among pediatric population of the country,
yet there are no authentic nationally representative data on exact incidence rate
of the illness. The etiology of the illness is diverse, and the currently employed
terminology, Acute Encephalitis Syndrome (AES), which has rendered a specific entity
to a constellation of diverse neurological diseases, some even non-infectious in nature,
seems misnomer. Admittedly, the purpose is to capture all neurological diseases presenting
in outbreak forms with special focus on surveillance of Japanese Encephalitis (JE).
1
1
Burden in India: Do we have reliable estimate?
One way to find burden of AES in India is through the website maintained by Directorate
of National Vector Borne Disease Control Programme (NVBDCP), Delhi.
2
However, here again the focus is JE, and all non-JE cases are clubbed under one head.
No details are provided on different etiological causes of AES. As per the latest
data, this year till October 31, 7201 cases and 989 deaths of AES are reported from
all over the country.
2
Then there are sporadic reports mainly from the different medical institutions on
incidence of AES or acute viral encephalitis, mainly among hospitalized children.3,
4, 5, 6, 7 There is paucity of population-based studies, as well as incidence rate
of a particular viral encephalitis. Most of the population-based studies have focused
on outbreak investigations and surveillance of AES. A recent review provides an overview
of these studies in some details.
8
2
Outbreak investigations: Another Achilles’ heel?
There is no ‘early warning’ or ‘alert system’ available in the country on any outbreak
of known or unknown entity. Most of the times, the media ‘break’ the news regarding
appearance of an outbreak. Here, the focus seems on ‘sensationalization’ with hidden
motive to harass health officials or institutions. These news items lack specificity
and details. The response of the health department and investigating agencies is also
equally shoddy and clumsy. The usual ‘knee-jerk reaction’ is to dub all these outbreaks
as viral encephalitis or JE. There is hardly any effort made to define a case properly,
a correct case definition is often lacking, teams work with a rigid mindset and complete
the ritual of collecting few samples. Lack of adequate research laboratories for virological
workup is lacking in the vicinity of most outbreaks, the delay in collecting, transporting
and processing the samples further make the entire process a redundant exercise. Autopsies
and detailed histopathological studies of viscera have almost become extinct now.
9
Another big flaw is to differentiate various outbreaks of AES on the basis of ‘primary’
versus the ‘secondary’ brain diseases. Here comes the significance of segregating
the latter from the former. A primary brain infection must be distinguished from a
secondary involvement of brain. Or in other words, ‘encephalitis’ from the ‘encephalopathy’.
It is of paramount importance not only to reach at a correct diagnosis, but also to
launch preventive measures at community level. There are instances in the past, when
an entirely a non-infectious entity was targeted for control with large scale vaccination
drive! Many outbreak investigations are terminated before reaching to their conclusive
ends. For example, investigations of outbreaks of acute brain diseases with high mortality
in Jamshedpur
10
and Nagpur
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in 50s are still inconclusive. Whether these outbreaks were indeed caused by some
viruses or were entirely non-infectious in nature is still undetermined.
12
There is a tendency to dub every outbreak involving fever with altered sensorium as
acute encephalitis or AES. Certainly, there are some ‘clues’ or ‘pointers’ that hint
to a diagnosis other than the acute encephalitis if followed judiciously.
13
WHO has also not provided any proper algorithm for outbreak investigations to those
engaged in the field. The major contributors to the broad group of AES should be identified
and compartmentalized.
3
Has JE lost its pre-eminence as a leading viral encephalitis in India?
Till quite recently, JE has been the center of all investigations pertaining to acute
encephalitis in India. In fact, as stated above, the term ‘AES’ was coined to facilitate
JE surveillance. However, in last decade or so, there is a shift in the spectrum of
causative organisms responsible for acute encephalitis in India.
8
Most studies have now reported non-JE etiology for AES in India; accordingly, enteroviruses,
rhabdoviruses, herpesviruses, paramyxoviruses, etc. are getting larger share.4, 5,
8 If one analyzes the data provided by NVBDCP, the JE constitutes from a meager 8.9%
of all reported AES in 2012 to 19.2% in 2015 till October, 2015
2
(Fig. 1
). It means non-JE viruses and some non-encephalitic illness, i.e. encephalopathies
are contributing chiefly to overall burden of AES in India. It seems that JE has now
acquired a regional status; its outbreaks are more circumscribed, and confined to
a limited geographical area, but are now mainly reported from a few states such as
Assam, West Bengal, Uttar Pradesh, and Jharkhand.
2
Of late, people have started questioning the prudence of continuing large scale JE
vaccination program in view of its focal nature, low burden, and uncertain effectiveness
of currently employed JE vaccine.
14
The vast group of illnesses contained in the non-JE group needs to be defined, if
we need to reduce the burden of AES in India. Mere relying on vector control and JE-vaccination
may not yield the desired results.
Fig. 1
Cases and deaths due to AES and JE in India, 2009–15.
Data from Directorate of National Vector Borne Disease Control Programme – Delhi.
4
Is existing surveillance competent enough to detect any new agent?
In recent times, many new viruses are detected from different regions of the world
that include Ebola, Crimean-Congo Hemorrhagic Fever, Middle East Respiratory Syndrome
Coronavirus (MERS-CoV), Zika virus, etc. Is our existing surveillance competent enough
to suspect and diagnose transmission of these novel agents? There are many instances
in recent past, when our investigating agencies and surveillance systems did very
sloppy investigations. Take the case of a lethal outbreak in Siliguri, which created
havoc among public and heath experts way back in January–February 2001. Several agencies
had investigated this peculiar outbreak and came out with their own interpretations
and results. Initially, it was reported to be caused by unidentified vial agent, later
atypical-Measles virus and Hantavirus infection were blamed, and ultimately, CDC,
Atlanta concluded that the outbreak was caused by Nipah/Hendra or closely related
virus!
15
There are instances when even premiere investigating agencies had failed to differentiate
a non-infectious entity with viral encephalitis. Investigations performed in Saharanpur
and adjoining districts of western UP and Uttarakhand, and Muzaffarpur, Bihar are
the most recent examples.
These illustrations highlight the significance of establishing a competent surveillance
system, which is well supported by sophisticated investigational facilities, capable
of handling and diagnosing new pathogens. A precious time is lost to institute appropriate
education, preventive and control measures. A timely intervention is the key to prevent
or minimize human losses. On global level, the success to curb an evolving pandemic
of SARS and more recently, successfully containing emerging Ebola outbreak in Africa
are shining examples of extraordinary swift and coordinated actions taken by global
health sectors, governments, and agencies.
5
What is needed?
Currently, we do not have a composite picture of overall burden of AES, or more precisely,
viral encephalitis in India. Merely clubbing all related illnesses under one head
is not sufficient. The time has come to move beyond, but presuming every case (or
an outbreak) of AES is yet another instance of acute viral encephalitis that in turn
is caused by JE virus may not serve the purpose. We need to invest heavily in building
a well performing AES surveillance system backed by state-of-the-art laboratory network.
Laboratories that perform routine testing for known pathogens responsible for viral
encephalitis should be established in every district's health headquarter. Routine
surveillance should be augmented and outbreak investigations must be bolstered. We
need a well coordinated, thorough systematic outbreak investigation approach with
correct methodology to investigate all the recurring outbreaks of unknown etiology
rather than clubbing them under one head of viral encephalitis and resorting to empiric
preventive measures like mass JE vaccination programs. There must be an official ‘early
warning’ or ‘disease alert’ system so that our reliance on media reporting and media
based investigations is curtailed. Our inability to deal with emerging pathogens or
even denying the existence of a problem or censoring the news of any new disease appearance
is not going to be rewarding in this era of information revolution. On the contrary,
it would bring bad name and erode our reputation among international health community.
Conflicts of interest
The author has none to declare.