Microcephaly can't be ruled out in Rajasthan Zika outbreak

Contributed by Dr Veeren Ganta, Dr Ashwini Tayade

Pune-based National Institute of Virology (NIV) has come out with a study on strains of Zika virus (ZIKV) that led to an outbreak in Rajasthan in 2018, and in Gujarat and Tamil Nadu in 2016 and 2017 respectively.

  • The NIV paper, to be published in 'Infection, Genetics and Evolution', said that mutation (S139N) leading to increased infectivity in humans causing microcephaly was not present, but "once ZIKV establishes in the Indian ecosystem, its chances of mutation (to other forms) cannot be neglected. Despite the absence of the proposed mutation on the transmission and microcephaly, the chances of not finding such a clinical condition cannot be guaranteed."
  • The paper further clarifies that a study done in Thailand by Wongsurawat et al. in 2018 found that despite the absence of this particular mutation, cases of microcephaly were reported. (Wongsurawat T, Athipanyasilp N, Jenjaroenpun P, Jun S, Kaewnapan B, Wassenaar TM, et al. Case of Microcephaly after Congenital Infection with Asian Lineage Zika Virus, Thailand. Emerg Infect Dis. 2018;24(9):1758-1761. https://dx.doi.org/10.3201/eid2409.180416)
  • The paper also says that presence of the reverse mutation (N139S) can cause milder neurovirulence, that is, it can affect the nervous system. Yadav confirmed its presence in Indian ZIKV sequence retrieved from Rajasthan.
  • More than 130 cases of Zika were reported in the last outbreak in Rajasthan, three in Gujarat and one in Tamil Nadu. More than 160 cases of Zika were reported in Madhya Pradesh as well.
  • The study, therefore, confirmed that in all the three cases — Rajasthan, Gujarat and Tamil Nadu — it was Asian lineage at work, and not African. Asked if the former is more harmful than the latter, Yadav said, “Experimental studies need to be performed in order to comment on the extent of harmfulness of the Asian as well as African strain.”