Tamil Nadu on Monday reported India’s fourth case of the Zika infection. A 27-year-old man from N Puttur village in Krishnagiri district had tested positive for the virus on July 1, though the state health secretary has said he has now recovered completely.

In May, health authorities had announced that three cases of Zika infections had been detected in two Ahmedabad localities earlier in 2017.

Like the three cases in Gujarat, the man from Krishnagiri also has no history of travel to foreign countries where the disease has been prevalent. “This means that it is a locally transmitted case,” said Tamil Nadu Health Secretary J Radhakrishnan, indicating that the virus may be locally present.

The Zika infection was detected during a routine health surveillance, during which people with fever were tested for the disease. None of the patient’s family members have tested positive for the infection, the health secretary said.

“It is an isolated case and there is no need to ring alarm bells,” Radhakrishnan said.

What is Zika?

The Zika virus is transmitted by the bite of the Aedes mosquito, but can also spread through sexual contact. It generally causes a mild and temporary infection in adults with symptoms such as fever and rashes.

However, Zika infections have also been linked to cases of Guillain-Barré syndrome – a nervous disorder caused by a person’s own immune system attacking nerve cells and causing muscles weakness and sometimes paralysis.

Pregnant women and their foetuses face the biggest danger from the Zika virus. Infections in pregnant women can lead to congenital defects in their newborns, such as microcephaly in which the infant’s brain is small and underdeveloped.

In November last year, the World Health Organisation had lifted the global health emergency that had been declared since early 2015, following Zika outbreaks in several countries. Brazil was the worst hit, with hundreds of children born with microcephaly.

Of the three cases reported in Gujarat, two were recorded in pregnant women. But Gujarat health officials have maintained that the children born to both women have not suffered any developmental deformities.