India at high risk of Zika, show travel, climate and transmission patterns

Sanchita Sharma, Hindustan Times, New Delhi, The 2.6 billion people living in many parts of Asia and Africa are at high risk of Zika infection,

predict scientists after analysing travel, climate and mosquito patterns in these regions.
Among the most vulnerable countries are India, China, the Philippines, Indonesia, Nigeria, Vietnam, Pakistan and Bangladesh, where the Aedes aegypti mosquito that spreads the infection also causes seasonal outbreaks of dengue, chikungunya and yellow fever.
The study was published online on Thursday in the journal, Lancet.
Though most people only have mild symptoms of fever, rash, conjunctivitis, fatigue and joint pain for two days to a week, but pregnant women are at risk of having babies with a birth defect called microcephaly — babies have unusually small heads — and other brain abnormalities.
With 26 million babies born in India every year and 80% of people infected not developing symptoms, the risk to babies in the womb is very high.
Though mosquitoes are the main vector, Zika can also be spread through sex and blood transfusions. There is no treatment or vaccine for Zika infection.
Experts, however, caution that the study may overestimate the number of people at risk because Zika may have had infected populations in some of these countries in the past, which would have led to people developing immunity against the virus.
Read| 13 Indians among Zika-hit people in Singapore, foreign workers affected
In February, the World Health Organization declared Zika a global emergency after its link with microcephaly in babies was established. Since then, it has affected more than 70 countries and infected more than 100 people, including 13 Indians, in neighbouring Singapore.
To figure out where Zika might gain a future foothold, researchers used dengue as a model to examine patterns of people travelling from infected regions in the Americas to Africa and Asia and combined that with an assessment of local conditions, including mosquito populations.
“No one has ever looked, so we don’t know if there is any pre-existing immunity to the virus,” said Dr. Abraham Goorhuis of the University of Amsterdam, an author of a commentary that accompanies the Lancet study. The virus in the Americas is an Asian strain that was responsible for a large outbreak in French Polynesia and other Pacific Islands in 2013 and 2014.
“If there was broad circulation of this virus in Asia, then it could be that the risk of Zika spreading to Asia won’t be as bad as we think,” Goorhuis said. Another unknown was whether people exposed to the African strain of Zika are protected once the slightly different Asian version arrives.
Goorhuis also noted it was possible Zika might eventually burn itself out after about a year or so of circulation, the way a related virus, chikungunya, recently did.