Authorities in India's southern Kerala region have issued a statewide alert after 14 cases of the Zika virus were detected, officials said.
Among the patients was a 24-year-old pregnant woman who was undergoing treatment at a hospital in the state capital Thiruvananthapuram.
Pregnant women are particularly vulnerable and can transmit the mosquito-borne illness to their newborns which can result in life-altering conditions such as Guillain-Barre syndrome, a rare auto-immune disease.
The woman tested positive yesterday and 13 more cases were confirmed today, state health minister Veena George said.
"All of them are healthcare workers and currently remain under medical care, but stable," she said.
Zika is mostly spread through the bite of the Aedes mosquito but can also be sexually transmitted, according to the US Centers for Disease Control and Prevention.
The virus was first discovered in monkeys in Uganda's Zika forest in 1947 and has caused several outbreaks across the world in recent decades.
No vaccines or anti-viral drugs are available as prevention or cure.
Symptoms include fever, skin rashes, conjunctivitis and muscle and joint pain, but fatalities are rare.
Indian officials said the pregnant woman infected had showed symptoms including fever, headache and rashes before being admitted to a hospital, where she safely delivered her baby on Wednesday.
The newborn tested negative for the virus, the minister said.
Health officials have been assigned to the area to monitor for any further cases while infection control teams were spraying chemicals to stop mosquito breeding.
India also saw Zika outbreaks in 2017 and 2018, with hundreds of cases reported in western Gujarat and Rajasthan as well as central Madhya Pradesh state, but the latest cases are the first for Kerala.
The state is currently battling a surge in Covid-19 cases, with more than 13,000 infections recorded today, the highest number of any Indian state.