Home / Opinion / Zika’s shadow over India

A dreaded new virus that deforms the heads and brains of foetuses in women’s wombs is at the subcontinent’s doorstep. There is no vaccine or medicine available, its cousins—dengue, chikungunya and other mystery viruses—are already ravaging India, and there is little India can do to keep it out.

Last week’s events in Singapore are the most recent reminder of the speed with which Zika is waltzing across the globe. In nine years, it has spread to 70 countries, following its peripatetic family, the Flaviviridae, borne by their mobile, ever-evolving host, the Aedes mosquito. Since it was detected in Brazil last year, the Zika virus has spread across the Americas. But its most damaging effects have been in Brazil, which now reports more than 1 million infections, including nearly 2,000 cases of microcephaly, babies born with abnormally small brains and heads.

Most of the 50 cases that flared in less than a week since Zika was detected in Singapore are mild (only one was a pregnant woman). Symptoms include rashes, fever, joint pains, headaches and red eyes. “We expect to identify more positive cases," a Singapore government statement said. Singapore’s Zika appears to have evolved locally, but either way, the city state is one of the world’s leading transit hubs, with more 50 million people funnelling through it every year, which means the virus will swiftly continue its globalization.

As of 24 August, 19 European countries reported travel-borne Zika infections, according to the latest update from the European Centre for Disease Prevention and Control. Currently, the effects of Zika—its first major outbreak reported in 2007 on the remote island of Yap in the western Pacific—are felt most in pregnant women, but there is no telling how the virus will turn, given that the evolution of the Flaviviridae and the Aedes mosquito have been inadvertently fast-tracked by humans.

This is how it works: Once creatures spread outside their previous range, they become an invasive species, none more than humans. “Because of all species, humans occupy the widest range of habitats on Earth, once a species evolves the ability to coexist with humans they will likely be spread by the great mobility of humans," wrote US biologists Jeffery Powell and Walter Tabachnik in Memórias do Instituto Oswaldo Cruz, a Brazilian biomedical journal, in December 2013.

When insects that require vertebrate blood learn coexistence, the most stable blood source is human, as the striped Aedes mosquito has learned. Among its accompanying viruses are dengue, chikungunya, yellow fever, west Nile fever, Zika and the relatively unknown Kyasanur forest disease (KFD)—the last caused by the Flaviviridae virus whose history illustrates the co-evolution of human, mosquito and virus.

Since 1957, when it was first isolated in a monkey in Kyasanur, Karnataka, KFD threw up a few hundred human cases every year. Since 2012, however, samples of the virus in humans and monkeys were found in Tamil Nadu and Kerala. Now, a sibling, the Alkhurma haemorrhagic fever virus, has been reported in Saudi Arabia, according to the US Centers for Disease Control. Since city physicians are not familiar with KFD, it is hard to detect in urban areas. Some of its symptoms—fever, chills, headache, muscle pain, low blood pressure and low platelet counts—mirror those of dengue, chikungunya and Zika.

Alongside, there are a host of unknown, evolving mosquito-borne ailments with some of these symptoms, confounding Indian physicians and hospitals. I spent almost two years with joint pains caused by one these mysterious ailments (a chikungunya-like virus, my doctor concluded, after a battery of inconclusive tests), and across cities like Bengaluru and New Delhi, stories of people struck down with similarly debilitating manifestations are common.

Locally or globally, mosquito-borne viruses are in various states of evolution and emergence, fuelled directly by the weapons we use against them, from pesticides to drugs. Between 5% and 20% of a mosquito population’s genome—the collection of their genes—is responding to evolutionary pressure at any given time, US and Russian scientists reported in June 2015 in the Proceedings of the Royal Society B, a biological research journal.

The domesticated mosquito has, in almost all cases, emerged from ancestral forest varieties, with distinct biological features and abilities. For instance, the genes of the Aedes aegypti mosquito—vector of chikungunya, dengue and yellow fever—have evolved so that it can recognize a compound present in human odour, a 2014 paper reported in the journal Nature, providing one of the first genetic insights into how some mosquitoes made the switch from animal blood. This mutated female Aedes—female mosquitoes are the world’s disease-spreading bloodsuckers—coexists in some parts of Africa with its old-world, arboreal cousin, which continues to prefer non-human blood.

The domesticated mosquito’s adaptation to humans, a paper in the June 2016 edition of the Journal of Vector Borne Diseases noted, is quicker and faster than ever. It appears now to be a question of when, not if, the Zika virus will arrive in India.

Samar Halarnkar is editor of Indiaspend.org, a data-driven, public-interest journalism, non-profit organization. He also writes the column Our Daily Bread in Mint Lounge.

Comments are welcome at frontiermail@livemint.com. To read Samar Halarnkar’s previous columns, go to www.livemint.com/frontiermail

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