Nation-wide vector surveillance on Zika and Dengue did not indicate transmission of the "American lineage pandemic ZIKA virus" in India

Objectives In wake of the Public Health Emergency of International Concern declared on ZIKA by the World Health Organization during 2016, Indian Council of Medical Research (ICMR) carried out countrywide vector surveillance for ZIKA and DENGUE viruses (ZIKV & DENV) in India, as a preparedness measure during 2016-2019. Methods High-risk zones distributed to 49 Districts in 14 states/ Union Territories (UT) were included in the study. Seven ICMR Institutions participated, following a uniform Standard Operating Protocol. Aedes specimens sampled on weekly intervals were processed by multiplex Reverse transcriptase PCR for ZIKV/DENV and Real-time RT-PCR of ZIKV (among few samples distributed to all Districts). Results Altogether, 79492 Aedes specimens in 6492 pools were processed and three (0.05%) and 63 (0.97%) pools respectively were found positive for ZIKV and DENV. ZIKV infections were recorded in Aedes aegypti sampled during 2018 sporadic ZIKA outbreak in Jaipur, Rajasthan. However, these belonged to the Asian lineage of the virus, already circulating in the Country. Both Ae. aegypti and Aedes albopictus distributed to 8 states/ UTs were found infected with DENV. Besides, both sexes of Ae. albopictus were infected indicating trans-ovarial transmission. Conclusion This investigation evinced no active transmission of the "American lineage - pandemic ZIKA virus" in India during the pandemic period.