ZIKV Outbreak in Thiruvananthapuram, Kerala, India, 2021 -A Primary Report

The recent global outbreaks of the ZIKA Virus (ZIKV) reported in 85 countries and territories caused severe complications such as microcephaly among neonates and Guillain-Barre Syndrome among the older population. Recently, an outbreak of ZIKV was reported from Thiruvananthapuram, the capital city of Kerala, India with about 70 confirmed cases. We conducted an outbreak investigation and the primary findings are described here. A cluster of ZIKV cases from the Kadakampalli / Anamugham administrative wards of the Thiruvananthapuram Municipal Corporation area was reported where Kerala Institute of Medical Sciences (KIMS) is located. Later many ZIKV cases were reported from other wards of the city. The density of known Aedes vectors was high in this region of the metropolitan city. Aedes albopictus, Aedes aegypti and Aedes vittatus collected from the focal area of the outbreak were found to be naturally infected with ZIKV. Male specimens of Ae . albopictus were naturally infected, indicating trans-ovarian transmission of the virus. This is first report of incrimination of Ae . albopictus and Ae . vittatus in ZIKV transmission from India. The virus was characterized and the partial sequences clustered with the Asian strain of ZIKV reported from India. The NS5 sequences of human and Ae . albopictus pools from Thiruvananthapuram were 100% similar indicating an ongoing active ZIKV transmission.