Two months after a 68-year old British man became sick with Zika virus, traces of the germ lingered in his semen, researchers reported Friday.

The finding suggests that the mosquito-spread virus may unexpectedly hang around in the body for much longer than symptoms appear, which typically only last for about a week. (Though only a quarter or so of people infected with Zika experience any symptoms.) The viral loitering may up the chances of transmission, the authors speculate.

The British man was infected with the virus while traveling to French Polynesia in 2014. Follow-up testing of the man found traces of viral genetic material in his semen 27 days and 62 days after he first reported symptoms of the infection, which included fever, lethargy, and a rash. The findings appeared Friday in Emerging Infectious Diseases.

"Although we did not culture infectious virus from semen, our data may indicate prolonged presence of virus in semen, which in turn could indicate a prolonged potential for sexual transmission of this flavivirus," the authors concluded.

The results follow recent news of a sexual transmission of Zika virus from a US man returning home from Venezuela, where Zika is currently circulating. Researchers have also reported that traces of Zika virus can be found in infected patients' urine and saliva, as well as blood and semen. However, public health experts suspect that sexual transmission and any other person-to-person transmission are rare. They emphasize that mosquito bites are still considered the main route of transmission.

The Zika virus, which is currently spreading throughout the Western Hemisphere, typically only causes mild symptoms. However, it's spread has triggered international alarm in light of mounting data that suggests the virus may be causing paralyzing neurological conditions in some patients and severe birth defects in babies born to infected mothers.

Emerging Infectious Diseases, 2015. DOI: 10.3201/eid2205.160107 (About DOIs).