COVID-19 patients have been known to suffer from a variety of aftereffects, including a loss of hair and the sense of smell.

Now, researchers are asking if COVID-19 could also cause male infertility. 

A team of Italian scholars said in a paper it released in March that 11 of 43 men who recovered from novel coronavirus infections, or one-quarter of the test subjects, were found to have either azoospermia, which means there is no sperm in semen, or oligospermia, a low sperm count.

The paper can be viewed at: https://academic.oup.com/humrep/advance-article/doi/10.1093/humrep/deab026/6125160

The researchers pointed out that COVID-19 could cause the sperm count to drop, while at the same time admitting their subject population is small.

“COVID-19 patients of reproductive age should undergo a careful follow-up exam for their reproductive function,” the scientists said in the article.

A pair of scientists from Germany and elsewhere also said they studied the semen of 84 men who recovered from novel coronavirus infections and 105 age-matched healthy men at 10-day intervals for 60 days.

They said in a paper published in January that the infected subjects showed significantly higher levels, than their healthy counterparts, of markers of inflammation and oxidative stress, which negatively impact sperm.

The paper is at: https://rep.bioscientifica.com/view/journals/rep/161/3/REP-20-0382.xml .

Mechanisms through which infectious diseases affect sperm is roughly divided into two categories.

One involves viruses entering the testes, where they attack spermatogonia, or cells that develop into sperm. The other involves high fever exposing the testes to heat and thereby killing sperm.

A rise of only 2 or 3 degrees in body temperature is enough to kill sperm. It is believed that males risk a drop in their sperm count just by staying too long under a “kotatsu,” a quilt-covered low table for keeping legs and feet warm.

The mumps virus, responsible for mumps, and the Zika virus, responsible for Zika fever, infect and attack testicular cells. Others, such as the influenza virus, cause sperm to die from high fever.

QUESTION OF VIRUS INTRUSION INTO TESTES

It has yet to be established which of the two mechanisms is at work with COVID-19. There are, however, reports suggesting that testicular cells have been infected with the novel coronavirus.

A group of Chinese researchers reported in April last year that cells in the testes have a protein called ACE2, which serves as a foothold by which the COVID-19 virus binds to a cell.

The results can be seen at: https://www.fertstert.org/article/S0015-0282(20)30384-8/fulltext.

That means testicular cells theoretically have the potential to be infected with the novel coronavirus. In fact, however, no virus was found by polymerase chain reaction (PCR) tests in the semen of any of the 34 COVID-19 patients who were studied.

A separate team of Chinese scientists said in May last year that COVID-19 virus was found by PCR tests in the semen of six out of a total 38 men who either had recovered or were still infected. The report is at: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2765654.

Still another group reported in December that autopsies of the testes of COVID-19 patients found traces of the coronavirus in their testicular cells. The report is at: https://www.nature.com/articles/s41423-020-00604-5.

No available report, however, has yet demonstrated that spermatogonia were ever infected with the COVID-19 virus. Masahiro Ito, a professor of anatomy with Tokyo Medical University, is therefore skeptical of the theory saying that the virus can directly infect testicular cells.

A novel coronavirus infection causes excessive immune response and inflammation in blood vessels. If it also damages capillary vessels in the testes, that could result in testicular inflammation, thereby causing spermatogonia to die or the virus to stray off into the testes.

To endorse that hypothesis, Ito called attention to a scientific article saying that red blood cells were found to have exuded from capillary vessels in the testes in COVID-19 patients and the concentration of lymphocytes was also found to have grown in their surroundings 

The article is at: https://www.sciencedirect.com/science/article/pii/S2589537020303485.

By contrast, Akira Tsujimura, a professor of urology with Juntendo University Urayasu Hospital, says he believes fever is the culprit because fewer available reports say that the virus was detected in semen than those that say no virus was detected.

Tsujimura, who is well-versed in male infertility, also said there should have been more reports on pain in, and swelling of, the testes if testicular cells were being infected.

He pointed out that, unlike annihilation of sperm due to heat, which is only a transitory phenomenon, destruction of spermatogonia by a virus is seldom repairable and can therefore have serious consequences.

“Little is yet known about the damage done to the reproductive function,” Tsujimura said. “Younger people should therefore take ample measures to prevent infections to the best extent possible.”