The US has reported the first case of the Zika virus being transmitted sexually, further raising fears over the potential spread of the disease.

The patient, in Dallas, Texas, was infected after having sexual contact with an ill individual who returned from a country where Zika virus is present, officials have confirmed.

The primary route of transmission is through the Aedes species of mosquito. “Now that we know Zika virus can be transmitted through sex, this increases our awareness campaign in educating the public about protecting themselves and others,” said Zachary Thompson, director of Dallas County Health and Human Services director. 

“Next to abstinence, condoms are the best prevention method against any sexually-transmitted infections,” he stressed.

Only 20% of those infected with the disease will experience any symptoms, the most common of which are fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting several days to a week.

However, the disease is thought to pose a serious risk to developing foetuses, having been linked to a neurological birth disorder called microcephaly which causes babies to be born with abnormally small heads. 

According to reports, cases of another neurological condition called Guillain-Barre Syndrome, that can cause paralysis, are also higher in areas hit by the virus.

The World Health Organisation has declared an international public health emergency, and has called for a coordinated international response to minimise the threat in affected countries and reduce the risk of further international spread.

News of the first sexually-transmitted Zika infection comes as Ireland reports its first two cases in people who had travelled to Latin America, following six cases in the UK and two cases in Australia.