What the latest Zika outbreak in India means

measuring microcephaly. Photo WHO

A small study undertaken at JIPMER has found Zika virus antibodies in 14 of 90 patients with Guillain–Barré syndrome. This indicates that there might be a remote possibility of Zika virus silently circulating in some parts of India and could cause an epidemic at some future date. Is the latest Zika virus outbreak in Jaipur, which is the third instance in less than two years, where 80 people have been infected, including 22 pregnant women, a sign of things to come?

With 80 laboratory-confirmed cases of Zika virus already in Jaipur, including 22 pregnant women, the latest outbreak is India’s most severe so far. In January 2017, three confirmed cases of Zika were reported from Ahmedabad, including a pregnant woman, and in July the same year a single case was reported from Tamil Nadu’s Krishnagiri district.

Unlike in the case of the Ahmedabad outbreak that was kept under wraps by the Health Ministry with even the World Health Organisation being informed only in May, there has been more transparency in the last two instances. That said, the WHO website on Zika virus disease outbreak still does not have any mention of the July 2017 outbreak and the latest one. About 4.5 lakh people at the outbreak site in Rajasthan have been brought under surveillance.

While steps to halt mosquito breeding have been initiated, it is to be noted that controlling breeding of the Aedes aegypti mosquito, which transmits the Zika virus, is very challenging. Controlling the spread becomes even harder as the mosquito is widely prevalent in India, and the infection remains asymptomatic in about 80% of cases, allowing the virus to silently spread from one person to another. It can also spread from a pregnant mother to the foetus. Even when the infection manifests itself, the symptoms are very mild and non-specific, thus making it difficult to correctly and easily diagnose it.

study published recently in the journal Neurology India found 14 of 90 patients with Guillain–Barré syndrome (a neurological complication seen in Zika-infected adults) in Puducherry-based Jawaharlal Institute of Postgraduate Medical Education and Research tested positive for Zika virus antibodies. Four of the 14 patients also tested positive for an anti-dengue antibody. There is a remote possibility that the Zika virus is silently circulating in some parts of India and could cause an epidemic at some future date.

It is not clear if the first person (index case) or others who had contracted the infection had travelled to any country where there is a risk of Zika virus infection. The absence of travel history outside India in the recent past by any of the infected individuals would indicate that the virus is already widely prevalent in the mosquito population. Spread through sex without multiple instances of infection by mosquitoes is quite unlikely, given the spurt in the number of cases within a narrow window of time in the small community.

Since Zika infection during pregnancy can cause severe birth defects, particularly microcephaly (small size of the head), all the 22 pregnant women who have been infected must be closely monitored. Also, as there is no cure for babies born with microcephaly, there should be special awareness campaigns to educate people living in the outbreak area to avoid sex, particularly with the intention of getting pregnant, till the outbreak is brought under control.

The long winter ahead in north India and the imminent onset of northeast monsoon in the eastern coast of India is conducive for the mosquito to multiply and spread. This calls for a high alert. How well the infection is contained in the next week weeks will determine if the outbreak remains confined to some parts of Jaipur or not.

Published in The Hindu on October 18, 2018