A woman in Maryland contracted the Zika virus in a possibly unprecedented way: She apparently got it from a male sex partner who showed no symptoms of infection, according to a federal report.

The most widely recognized source of the infection is through the bite of an infected mosquito.

A section of the Morbidity and Mortality Weekly Report, released Friday by the Centers for Disease Control and Prevention, said only one other case has been reported in which a man without symptoms might have transmitted Zika to a female through sex.

But in that case, the report said, she could have been infected by a mosquito while traveling.

The report said it might be wise to expand the category of those considered exposed to include sex partners of people returning from areas with ongoing transmission of the Zika virus, even if the partners show no symptoms.