The Center for Disease Control and Prevention in the United States has cautioned pregnant women against travelling to Rajasthan due to an outbreak of the Zika virus. At least 153 cases of the virus were reported in the state in October and November, The Indian Express reported on Thursday.

The CDC, in an advisory issued on December 13, said the virus was endemic to India and pointed out “there is an unusual increase in the number of Zika cases in Rajasthan and surrounding states”. It cautioned pregnant women against travelling to such areas. “This is because Zika infection during pregnancy can cause serious birth defects,” the advisory added.

The public health institute said all travellers to areas with risk of Zika infection should prevent mosquito bites, and use condoms while having sex. “They should continue to take these precautions after their trip to stop the spread of Zika to others back home,” it added.

Women considering pregnancy should wait at least three months after returning to the US from Zika-affected areas before attempting to conceive, the advisory said. Men should wait for three months because Zika can stay in semen longer than in other body fluids, it added.

The Indian Express reported that tourism in Rajasthan might be affected due to the advisory. It quoted unidentified individuals from the tourism sector as saying that the peak tourist season for Rajasthan lasts from October to March. “One of the reasons behind this increase in footfall is the number of holidays during the period,” Sanjay Kaushik, a Jaipur-based tour operator, told the newspaper.

Between October and March events such as the Pushkar fair, Jaipur Literature Festival, Holi and Gangaur fair in Jaipur attract large numbers of tourists. According to state tourism department data, 35.34 lakh Indian and foreign tourists visited Rajasthan in December 2017, and 31.73 lakh people during the same month in 2016.

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.