Scientists at the National Institute of Virology (NIV), Pune, have raised an alarm about the spread of the Zika virus, along with dengue and chikungunya, across several States and Union Territories where it has never been reported earlier, establishing local transmission in India.
With the monsoon season, scientists have called for urgent strengthening of surveillance, after the circulation of Zika virus was detected in Delhi, Jharkhand, Rajasthan, Punjab, and Telangana in 2021, in addition to Kerala, Maharashtra, and Uttar Pradesh.
Previously, sporadic cases were reported from Gujarat (2016-17), Tamil Nadu (2017), Madhya Pradesh and Rajasthan (2018). The researchers also found co-infection of Zika, dengue and chikungunya, which, they said, was another concern at many places. There was a need to be aware and take preventive measures, they added.
Zika virus (ZIKV), a vector-borne flavivirus, is transmitted by the bite of infected Aedes mosquitoes, mainly Aedes aegypti and Aedes albopictus.
For the study, a total of 1,520 clinical samples — serum (1,253), plasma (99), whole blood (120), and urine (48) — were collected from 1,475 patients across 16 viral research and diagnostic laboratories (VRDLs) in Delhi, Kerala, Punjab, Rajasthan, Uttar Pradesh, Uttarakhand, Madhya Pradesh, West Bengal, Bihar, Odisha, Telangana, Assam, Jharkhand, and Bihar.
The samples were subsequently transferred to the apex laboratory at the Indian Council of Medical Research-National Institute of Virology (ICMR-NIV), Pune, for molecular diagnosis, serology, and genomic analysis.
“In 2021, Zika virus outbreaks were reported in Kerala (May-July), Maharashtra (July), and Uttar Pradesh (October) and since these outbreaks were reported from distant locations and over a period of six months, we conducted a retrospective screening of dengue and chikungunya negative clinical samples (stored with VRDLs) from May to October 2021 to understand the extent of the spread of the virus in India,” said Nivedita Gupta, head of virology at ICMR, who co-ordinated the study.
Pragya D. Yadav, scientist and group leader at the maximum containment laboratory at ICMR-NIV, added that after 2020, the public health surveillance of ZIKV could not be continued with the same vigour due to the involvement of all VRDLs in COVID-19 diagnostics considering the subsequent waves of the pandemic. All these VRDLs were advised to store the dengue/chikungunya test samples.
The research noted that retrospective surveillance for ZIKV demonstrated the silent spread of the virus to almost all parts of India with a predominance of the more recent 2018 Rajasthan ZIKV strain.
“Our results indicated the need for continuous and enhanced surveillance for ZIKV along with DENV [dengue virus] and CHIKV [chikungunya virus] with emphasis on the ante-natal ZIKV screening,” Dr. Yadav said.
The scientists added that the development of quick and reliable tests as well as validating the utility of simple serology-based tests for ZIKV would help in augmenting the diagnostic capabilities. With the massive upscaling of the COVID-19 RT-PCR testing laboratories in India, this network can also be re-purposed for augmenting ZIKV testing in the country.
“Along with these efforts, it is also essential not to lose sight of effective vector control measures and focus on the development of a safe and effective vaccine for ZIKV, which could be administered to pregnant women,” the study added.
