Traces of the novel coronavirus have been found in the semen of several infected men, according to a new study out of China’s Shangqiu Municipal Hospital that was published in the JAMA Network Open.

This finding raises the possibility that the virus might be sexually transmitted, although the small study didn’t conclude whether such transmission was possible.

Of the 38 men hospitalized with laboratory-confirmed COVID-19, doctors were able to determine that six of the patients, ranging in ages 20 to 60, had the virus in their semen. Four were still considered very sick with the contagion, while the other two were on the road to recovery.

“The presence of viruses in semen may be more common than currently understood, and traditional non-sexually transmitted viruses should not be assumed to be totally absent in genital secretions,” the study’s authors wrote.

Since there were no follow-ups to the short-lived study, it is not known how long the coronavirus can remain in semen or if the patients can transmit it to their partners during sex.

The study was led by Dr. Weiguo Zhao of the People’s Liberation Army General Hospital in Beijing.

Previous studies have shown that infectious viruses can be commonly found in semen, with Zika and Ebola being two notable recent examples. Researchers in China have claimed that 27 different viruses have been detected in human semen.

The new results contrast with a study of 34 Chinese COVID-19 patients that was published last month in the journal Fertility and Sterility.

U.S. and Chinese researchers found no evidence of the virus in semen. The patients were tested between eight days and nearly three months after the initial diagnosis.

Despite the findings from the new study, infectious disease experts have warned that does not establish concrete evidence that COVID-19 can be sexually transmitted. More research is still needed to provide a definitive answer.

The American Society for Reproductive Medicine also said it is important to keep the new study’s findings in perspective. However, to be on the safe side, “it may be wise to avoid sexual contact with men until they are 14 days without symptoms,” Dr. Peter Schlegel, the group’s immediate past president, said in a statement.

Medical experts believe that COVID-19 mainly spreads from droplets produced when infected people cough, which are then inhaled by individuals nearby.

Ethen Kim Lieser is a Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek and Arirang TV. He currently resides in Minneapolis.