Zika virus: Current concerns in India

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Date: May 2017
From: Indian Journal of Medical Research(Vol. 146, Issue 5)
Publisher: Medknow Publications and Media Pvt. Ltd.
Document Type: Report
Length: 2,684 words
Lexile Measure: 1470L

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Byline: Sumit. Bhardwaj, Mangesh. Gokhale, Devendra. Mourya

With confirmation of Zika virus (ZIKV) presence in India, screening of a large number of febrile illness samples yielded only four positive cases. In this review, we address the current concern with context to India. The possible reasons for low level of Zika prevalence in India have been discussed, by extracting some probable explanations from previous experience of chikungunya virus-vector model/studies. In the current context, it is hypothesized that Indian mosquito strains have lower susceptibility gradient/threshold for ZIKV. The very low positivity in the humans also indicates low levels of mosquito-human-mosquito transmission cycle. There is also a need to look for the existence of any such animal cycle/sylvatic involvement in India. The recently detected four cases in India show local transmission of ZIKV suggesting that ZIKV might have been present in India since long time. The earlier vector-virus relationship studies with chikungunya suggested that in due course of time, ZIKV might become a major public health concern in the future.

Introduction

Since 2013, with the first reported Zika virus (ZIKV) outbreak in the Marquesas Islands [1] and its subsequent spread to Brazil in May 2015[2], health agencies in India have been on alert and kept a watch on the Zika situation in India. There was anticipation that a ZIKV outbreak in India was possible due to the ubiquitous presence of the vector, Aedes aegypti mosquitoes and the susceptible host. On May 15, 2017, the Ministry of Health and Family Welfare, Government of India, reported three laboratory-confirmed cases of ZIKV disease from Bapunagar area, Ahmedabad, Gujarat, India [3]. The cases were confirmed by real-time reverse transcription polymerase chain reaction (RT-PCR) test [4]. Before this declaration, India was in WHO category-4 (virus may be present but no notified cases documented), but with these three confirmed cases, India has shifted to WHO category-2. Our previous review on Zika [5] provided the epidemiological background and algorithms to handle the ZIKV outbreaks in India. With recent confirmation of one more Zika case from Chennai in India [6], and after screening of a large number of febrile illness samples, yielded only four positive cases. The present review addresses the current concerns with context to Zika virus disease in India and why it has not been detected in a large number of individuals and what may be the risks involved in the future.

As evident from the present cases, Zika may not be a recent introduction in India. In 1954, National Institute of Virology (NIV), Pune (then Virus Research Centre), had tested samples from Bharuch district, which showed ZIKV antibody detection in 16.8 per cent of the samples [7]. However, due to high cross-reactivity of ZIKV with dengue virus (DENV) and other flaviviruses, it was difficult to confirm Zika virus infection in India based on serology. Three cases identified in Gujarat and one in Chennai did not reveal any travel history to ZIKV endemic region, suggesting that the ZIKV is not a recent introduction into the country and it may...

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Gale Document Number: GALE|A530058756