A new study, published in Fertility & Sterility, a peer-reviewed journal published by the American Society of Reproductive Medicine, claims that COVID-19 is unlikely to be spread through semen. According to University of Utah Health scientists who participated in an international study of Chinese men who recently had the disease, there was no evidence of the virus that causes COVID-19 in the semen or testes of the men.

However, the latest study was not comprehensive enough to completely rule out the possibility the disease being sexually transmitted. The researchers said that based on this limited research, the chances of it occurring appear to be remote.

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Effect on man's long-term reproductive health

James M. Hotaling, M.D., a co-author of the study and a University of Utah Health associate professor of urology specializing in male fertility, said: "The fact that in this small, preliminary study that it appears the virus that causes COVID-19 doesn't show up in the testes or semen could be an important finding."

"If a disease like COVID-19 were sexually transmittable that would have major implications for disease prevention and could have serious consequences for a man's long-term reproductive health," Hotaling added.

The study was launched by the international team of researchers from China and the United States in response to concerns that SARS-CoV-2, the virus that causes COVID-19, could be sexually transmitted like Ebola, Zika and other emerging viral pathogens.

As a part of the study, the researchers collected semen samples from 34 Chinese men one month (on average) after they were diagnosed with mild to moderate cases of COVID-19. Laboratory tests did not detect SARS-CoV-2 in any of the semen samples. However, the researchers noted that just because the virus wasn't present in the existing semen didn't necessarily rule out that it hadn't entered the testes where sperm cells are formed.

Impact on sperm production

Jingtao Guo, Ph.D., a postdoctoral scientist at the Huntsman Cancer Institute at the University of Utah who also co-authored the study, said: "If the virus is in the testes but not the sperm it can't be sexually transmitted. But if it is in the testes, it can cause long-term damage to semen and sperm production."

In order to get a clearer picture, the researchers analysed a dataset that generated from a single cell mRNA atlas from healthy young organ donors that was available from prior work. This atlas allowed the experts to examine mRNA, the genetic material used to make proteins, in any single testicular cell.

Following the dataset examination, the researchers found that the genes encoding the relevant two proteins were only found in four of the 6,500 testicular cells, suggesting that SARS-CoV-2 is unlikely to invade human testicular cells, Guo says.

Despite the results, the researchers acknowledge that their study has several important limitations including a small sample size and the fact that none of the donors had been severely ill with COVID-19.

Hotaling said: "It could be that a man who is critically ill with COVID-19 might have a higher viral load, which could lead to a greater likelihood of infecting the semen. We just don't have the answer to that right now. But knowing that we didn't find that kind of activity among the patients in this study who were recovering from mild to moderate forms of the disease is reassuring."

However, Hotaling also warned that intimate contact may still increase the risk of spreading the disease through coughing, sneezing and kissing. In addition, some infected people are asymptomatic and can appear healthy, even as they pass the virus along to others.