• The Zika virus that infected 159 people in an outbreak in Rajasthan last year, could have been circulating in India for several years and is endemic to Asia, according to a new study published in the journal Infection, Genetics and Evolution this week.
  • It suggests that people in the region may have been previously exposed to the virus, building herd immunity that may limit future outbreaks.
  • During the latter half of 2018, India recorded its first major Zika outbreaks in Rajasthan and Madhya Pradesh.
  • Around then, the ICMR said the Rajasthan virus had been sequenced and was closely related to a virus that had caused large epidemics and birth defects in Latin America in 2015.
  • Then, in November 2018, the Ministry of Health and Family Welfare issued a press release, citing the NIV’s research, to say that “known mutations” for foetal microcephaly were not present in the Rajasthan strain.
  • This week’s publication contradicts the the ICMR’s previous statements in two ways. First, it indicates that the Rajasthan Zika strain is not closely related to the Brazilian one.
  • While this is good news, because it implies that a portion of the population could be immune, it could also mean that Zika-related birth defects such as microcephaly were occurring even before the virus was first detected in India.
  • While endemicity means that large outbreaks, such as the Brazilian one, may not occur in India, serosurveys are needed to confirm this.