With 80 laboratory-confirmed cases of the 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 (even the World Health Organization was informed only in May), there has been more transparency in the last two instances. 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 the breeding of the Aedesaegypti 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, making it difficult to correctly and easily diagnose it. A study published in the journal Neurology India found 14 of 90 patients with the Guillain–Barré syndrome (a neurological complication seen in Zika-infected adults) in the 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 virus is circulating in some parts of India and could cause an epidemic at some point.
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 Zika infection risk. The absence of travel history outside India in the recent past by any of the infected individuals indicates the virus is prevalent in the mosquito population. Spread through sex, without multiple instances of infection by mosquitoes is unlikely, given the spurt in the number of cases within a narrow time window in a small community. Since Zika infection during pregnancy can cause severe birth defects, particularly microcephaly (small size of the head), all the 22 pregnant women infected must be monitored. Also, as there is no cure for microcephaly at birth, there should be campaigns to educate people living in the outbreak area to avoid sex, particularly with the intent of getting pregnant, till the outbreak is under control. The long winter ahead in north India and the imminent onset of the northeast monsoon in the eastern coast of India is conducive for the mosquito to multiply and spread. This calls for a high level of alert.