Experts fear the Zika virus, which has been linked to brain damage in unborn babies, may be transmitted through sex.
Zika is known to be spread by mosquitos bites and has spread rapidly through Brazil and other South American countries since late 2015.
While it manifests itself as a relatively harmless fever in most patients, it has also been linked to a spike in microcephaly – a condition causing babies to appear to have shrunken heads.
Health officials across the world have warned pregnant women in affected South American countries to take precaution to protect themselves from mosquito bites, with some advising women to put off becoming pregnant.
However, two cases of the virus in medical literature suggest that Zika may also be spread through during sex, prompting experts to call for further investigation into the possibility.
The only known cases of the virus being detected in a man’s semen involved a 44-year-old Tahitian man who contracted Zika during a drink to French Polynesia in 2013, The New York Times reported.
While his blood was clear, French investigators found traces of the virus in his semen and his urine.
The second case was that of Dr Brain D Foy, an expert in insect-borne diseases at Colorado State University, who unwittingly developed the virus after he travelled to Senegal to collect mosquitos for a study. Both he and his colleague who accompanied him fell ill with a fever when he returned to the US.
Days later, Dr Foy’s wife, a nurse, displayed similar symptoms including headache pains, a rash, and bloodshot eyes.
However, what had infected the three was unclear after the blood samples tested for malaria, dengue fever and yellow fever returned negative.
On the suggestion of another scientist, Dr Foy had the blood samples re-tested and found that he and his colleague, as well as his wife who had remained in the US, had been infected by Zika.
Dr Foy relayed his experience of the virus in the journal ‘Emerging Infectious Diseases’.
Research into Zika is further complicated by the fact that it does not infect common lab animals such as rats and mice, meaning controversial trials on monkeys may need to be used to investigate the condition.
Dr. William Schaffner, chief of preventive medicine at Vanderbilt University Medical School told The New York Times that while two suspected cases do not warrant a health warning from public health officials, he said: “it certainly should be studied.”
However, the World Health Organisation has sought to quell fears and said that
“Zika has been isolated in human semen, and one case of possible person-to-person sexual transmission has been described" but added: "more evidence is needed to confirm whether sexual contact is a means of Zika transmission.”
“The role of Aedes mosquitoes in transmitting Zika is documented and well understood, while evidence about other transmission routes is limited,” it said.
Health officials at the US Centers for Disease Control and Prevention have also said the two apparent instances are a “theoretical risk” and there is insufficient evidence to issue a warning about any concern that the virus may be spread through sex.
Dr Márcio Nehab, a paediatrician and infectious disease specialist at the Fiocruz research institute in Rio de Janeiro said that researchers should focus their efforts on mosquitoes.
"We still need a lot of study to conclude that sexual transmission can happen because little is known about the Zika virus.
"At the moment, we have to care more about the known vector, which is the mosquito, as the virus transmission route,” he said according to MailOnline.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies