Taking guard on Zika
The Hindu
December 02, 2018
Balram Bhargava
The disease spectrum of Zika
ranges from asymptomatic or mild illness to severe birth defects, including
brain damage and microcephaly in newborns.
Every year, several lives
across the world are lost or debilitated due to vector-borne diseases such as
dengue and chikungunya. In India, the first case of dengue was detected in 1964
in Kolkata, with numbers rising due to a lack of vector control, unplanned
urbanisation, climate change and varying immunological reasons. The same holds
true for chikungunya, another debilitating mosquito-transmitted disease. After
remaining incipient for almost 32 years, chikungunya re-emerged as a deadly
infection, in 2006, with more than 1.5 million cases reported in India, and
causing deaths or long-lasting physical impairment in millions of individuals
around the globe.
While India struggled with the
double burden of dengue and chikungunya, a covert virus called Zika sprang into
action. Zika was first discovered in monkeys in Uganda in 1947 and remained
dormant for several decades. India had gathered its first evidence of Zika in
1954, through a preliminary study conducted by the Indian Council of Medical
Research’s (ICMR) National Institute of Virology (NIV) in Pune. Limited
knowledge suggested that the Zika virus caused a milder form of dengue viral
illness: low grade fever, headache and malaise in 20% of infected individuals,
whereas 80% of those infected remain asymptomatic.
The African strain of Zika
transformed itself and in its new ‘avatar’, caused major outbreaks in the Yap
islands and French Polynesia in 2007 and 2013, respectively. While the world
was still oblivious of its potential, Zika became relentless with reports of a
sudden, unexplained spike in the number of babies born with microcephaly (small
heads) and brain damage in Brazil and other parts of Latin America, baffling
public health professionals. Prior to this outbreak, there was very limited
research on Zika, with about 15 10-15 articles describing the accidental
outbreaks in humans. Today, there are more than 5,000 published research
articles, highlighting the urgency to address the situation.
The disease spectrum of Zika
ranges from asymptomatic or mild illness to severe birth defects, including
brain damage and microcephaly in newborns, and Guillain-Barre Syndrome, a
dreaded post-viral neurological syndrome causing partial or complete paralysis
in adults. Unlike dengue, Zika can pass through the placenta of pregnant women
and infect the foetus, causing severe neurological damage. Unlike dengue, Zika is
also transmitted through the sexual route, i.e. having unprotected sex with an
infected individual. There is also a risk, of acquisition of Zika after blood
transfusion from an infected individual. The complexity of tackling Zika is
augmented by the absence of a vaccine or drug to prevent/treat the infection.
Zika was declared a public
health emergency by the World Health Organisation (WHO) in 2016. The Ministry
of Health and Family Welfare designated the ICMR with the task of setting up
human and mosquito surveillance for Zika Virus Disease (ZVD) in India. The
first case was confirmed by surveillance by the ICMR, in Ahmedabad, Gujarat, in
November 2016. Subsequently, three more cases: two from Gujarat and one from
Tamil Nadu were reported through ICMR surveillance. The Gujarat strain was
partially sequenced by ICMR-NIV and found to resemble the Zika strains from
Malaysia in 1966, which seemed to have relatively low outbreak potential and
led to the belief that it may not cause great damage.
Need for multiple engagement
However, this was far from the
reality. The ICMR’s surveillance detected the onset of a major outbreak of ZVD
in Jaipur city in September 2018. Itsoutbreak expanded rapidly and its control
became a challenging task. Many pregnant women also tested positive. However,
it is critical to understand that the positive number of ZVD cases may be the
tip of the iceberg, given the asymptomatic nature. It is possible that high
population mobility resulted in a spread of ZVD to parts of Gujarat and Madhya
Pradesh. While Jaipur has not reported new cases since October 29, 2018,
reports of sporadic cases have been trickling in from Gujarat.
There is also
active ZVD transmission ongoing in Bhopal and its neighbouring districts.
Genetic sequencing of the Jaipur Zika strain has revealed a close resemblance
to the deadly outbreak strain in Brazil. But a sequencing of the Rajasthan Zika
strains has shown that the known mutation for microcephaly is not present in
these strains. But maintaining a high vigil is a must as the absence of these
mutations does not rule out the possibility of microcephaly —the virus may
mutate in future or other unknown factors may interplay.
This wakeup call highlights
the need for multi-sectoral engagement with implementing agencies to achieve
effective vector control, and protect us from ill-health, economic losses and a
compromised future.
Dr. Balram Bhargava is
Director General, Indian Council of Medical Research (ICMR), New Delhi
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