Austin: The first US case of the Zika virus having been transmitted from human to human through sex has been recorded in Dallas County, local health officials said on Tuesday.

They added there are no reports of the virus being locally transmitted by mosquitoes in the Texas county.

Dallas County Health and Human Services said the case in Dallas was acquired through sexual transmission, adding that it received confirmation of the infection from the US Centres for Disease Control and Prevention.

The county did not identify the person infected. The CDC said it did not investigate how the virus was transmitted.

There have been six confirmed travel-related cases of Zika virus disease, all among residents of Harris County, where Houston is located, the Texas Department of State Health Services said.

Aedes aegypti mosquitoes, which carry the Zika virus, sit in a petri dish at the Fiocruz institute in Recife, Brazil. Photo: AP

In medical literature, there has been only one case of Zika transmitted sexually and one case in which the virus was detected in semen.

Zika virus poses relatively little threat to adults, with the majority of people infected displaying no symptoms. But there is more concern for pregnant women, with the virus linked to microcephaly – a condition in which babies are born with an abnormally small head.

The virus is commonly caught when bitten by an infected mosquito. In Australia, there is only one breed of mosquito which carries the virus, which only lives in tropical areas of far north Queensland.

Reuters