The Union Ministry of Health and Family Welfare sounded an alert on Sunday after a man from Bihar’s Siwan district tested positive for the Zika virus, the Hindustan Times reported. Pankaj Chourasia, 22, is a student of computer science in Jaipur. He had visited Siwan from August 28 to September 12.

The Zika virus is mainly transmitted by Aedes mosquitoes, including Aedes aegypti that carries dengue. Most people infected with Zika will show no symptoms or will have only mild symptoms of fever, rash, joint pain, conjunctivitis and, possibly, muscle pain and headaches that may last for several days to a week.

“The central surveillance unit of the ministry of health and family welfare notified us today about the Zika-positive patient who had visited Bihar,” State Health Society Epidemiologist Dr Ragini Mishra said on Sunday. After the Centre’s alert, the Bihar health department immediately sent a team to Siwan to put Chourasia’s family members under surveillance, she added.

“None of Chourasia’s family members showed symptoms of the Zika virus,” Mishra said. However, she added that as one of the family members is pregnant, the whole family will be kept under surveillance for 26 days.

Mishra said that the state health department has asked all districts to report cases of fever and microcephaly. According to the World Health Organisation, microcephaly is a condition where a baby has a head size much smaller than other babies of the same age and sex. This condition may be caused by Zika virus infection during pregnancy.

“They have been told to send all such samples to the viral research and diagnostic laboratories for confirmatory tests of rare virus strains like Zika,” she added.

An unidentified health ministry official said the department had discovered that Chourasia contracted the virus in Siwan district itself. “There has been additional fogging and the person has been kept under home-based isolation and extreme care is being taken,” he added.

In September, Rajasthan had recorded its first case of Zika virus infection after a woman tested positive in Jaipur.