The Zika virus strains collected in Rajasthan’s capital Jaipur do not have the mutations linked to fetal microcephaly – a serious birth defect in newborns delivered by women infected with the disease – PTI quoted the Union Ministry of Health as saying on Saturday.

“Advanced molecular studies of Zika virus strains, carried out through Next Generation Sequencing, suggest that the known mutations linked to fetal microcephaly and high transmissibility of Zika virus in Aedes mosquitoes are not present in the current Zika virus strain that has affected Rajasthan,” the ministry said. The strains were sequenced at the Indian Council of Medical Research’s National Institute of Virology in Pune.

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However, the government said it was monitoring the possibility of infected women delivering children with fetal microcephaly if the Zika strains mutate in future, or if other factors play a role.

The health ministry said around 2,000 samples have been tested so far, of which 159 were found to be positive. Adequate numbers of testing kits have been provided to viral research and diagnostic laboratories in the state. At least 50 of those infected with the virus are pregnant women.

In January 2017, Ahmedabad in Gujarat reported the country’s first outbreak of the virus strain. Another outbreak was reported in Tamil Nadu’s Krishnagiri six months later. The Centre later said the outbreaks had been contained.

The Zika virus is transmitted mainly by Aedes mosquitoes, including Aedes aegypti, which also carries dengue. Most infected people either show no symptoms or only mild symptoms such as fever, rash, joint pain, conjunctivitis and, possibly, muscle pain and headaches that may last a week.