Men who have recovered from COVID-19 may be at risk of developing low sperm count, at least in the short-term, a small new study suggests.
The study researchers, from the University of Florence in Italy, analyzed semen samples from 43 men ages 30 to 65 about one month after they had recovered from COVID-19. They found that 25% of the men had low sperm count, and nearly 20% had azoospermia, or the total absence of sperm in semen. That's much higher than the prevalence of azoospermia in the general population worldwide, which is around 1%, according to Johns Hopkins School of Medicine.
Moreover, participants with serious COVID-19 infections — those who were hospitalized or admitted to the intensive care unit (ICU) — were more likely to have azoospermia after their infection, compared with those who faced less serious infections, according to the study, published Feb. 1 in the journal Human Reproduction.
However, the researchers stress their study doesn't prove that SARS-CoV-2, the virus that causes COVID-19, harms sperm. The researchers don't know what the men's sperm counts were before their infections, so the authors can't say for sure if the counts declined post-infection; but all of the men with azoospermia had previously fathered children, which means they had at least some viable sperm in the past, the report said. In addition, it's possible that some of the medications given to treat COVID-19, such as antivirals, antibiotics and corticosteroids, could affect sperm counts.
Being sick in general may have an effect on semen. "The sicker you are, the more effect it can have," said Dr. Ajay Nangia, professor and vice chair of urology at the University of Kansas Medical Center, who was not involved in the study.
Dr. Boback Berookhim, director of Male Fertility & Microsurgery at Lenox Hill Hospital in New York City, agreed. "This may not be a specific COVID phenomenon and may (and is probably likely!) be due to these patients having a more severe illness [and requiring] intensive care," Berookhim told Live Science in an email.
Nangia added that these men need to be followed for a minimum of 90 days after illness to see if the effect is long-lasting, because sperm takes several months to fully mature. "You would have to repeat the study on these people at the 90-day mark," to know if the effect is prolonged, he said.
Related: Sexy swimmers: 7 facts about sperm
COVID-19 and fertility
There's reason to think that SARS-CoV-2 could affect sperm production. Testicular cells have high levels of the ACE2 receptor, which allows SARS-CoV-2 to get inside cells, the authors said.
However, only a handful of studies have looked for SARS-CoV-2 in semen from men who tested positive for the virus; those studies found the coronavirus in semen from some, but not all, of the men during infection or recovery.
For the new study, the researchers collected saliva, urine and semen samples from the participants about 30 days after they had recovered from COVID-19, which was defined as having two consecutive negative COVID-19 tests.
Of the 43 patients, 12 were treated at home, 26 were hospitalized and five were admitted to the ICU.
Overall, eight men had azoospermia and three had oligospermia, or low sperm count, defined in the study as less than less than 2 million sperm per milliliter of semen. (Men are generally considered to have a low sperm count if they have fewer than 15 million sperm per milliliter of semen, according to the Mayo Clinic.) The risk of azoospermia was linked with the severity of the men's illness: azoospermia was found in four out of five of the ICU patients, three of the 26 hospitalized patients and just one of the non-hospitalized patients.
Just one participant had SARS-CoV-2 detected in their semen, suggesting that "the occurrence of virus in semen is a rare event," after recovery, the authors wrote.
The researchers also found that three-quarters of the participants overall and 100% of the participants admitted to the ICU had high levels of interleukin 8 (IL-8), an immune system molecule and marker of inflammation, in their semen.
"COVID-19 patients of reproductive age should undergo a careful follow-up for reproductive function and semen parameters," the authors concluded.
Nangia said that based on the current study and other previous research, there appears to be at least a temporary effect of the illness on the testicles and sperm. "In the short-term, it looks real," Nangia, who is also a urologist with The University of Kansas Health System, told Live Science. However, the big question is whether the men's sperm sperm counts will increase over time. "Is it a persistent, irreversible effect? ... We don't know."
Berookhim said he's not convinced that patients who have been infected with COVID-19 necessarily require prolonged follow-up to analyze their sperm. But "we clearly need more data and experience dealing with the aftermath of COVID, and so more follow-up will help to better define which patients are most at risk for negative reproductive effects due to COVID 19," he said.
Certain viral illnesses are known to have a long-lasting effect on fertility. In particular, mumps can lead to inflammation of the testicles, known as orchitis, which can result in infertility in some cases. Nangia noted that there have been some reports of men with COVID-19 experiencing testicular pain similar to what's seen in mumps.
Although the new study is one of the largest to date to look at semen quality after COVID-19, it is still relatively small, the authors said, and so larger studies are also needed to confirm the findings.
Originally published on Live Science.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.