If you’re a male and you thought little of this pandemic until now, this new study should get your attention. According to researchers at the University of Hong Kong, unvaccinated hamsters that were infected with the coronavirus had shrunken testicles, resulting in an “acute decrease” in sperm count and testosterone.

While humans are certainly very different from hamsters, and the findings might not translate across species at all, this news is worrisome considering previous reports of COVID-related effects on testicular health and sexual performance.

A 2021 study by researchers at the University of Science and Technology of China found that male COVID-19 patients who recently recovered from their infection had significantly lower “sperm count, sperm concentration, and percentages of motile and progressively motile spermatozoa” compared to controls who were never infected. Another study from the University of Miami reached a similar conclusion, finding that men who had tested positive for SARS-CoV-2 had an almost five times lower sperm count in their ejaculate than men who hadn’t been infected. Elsewhere, at the University of Rome Tor Vergata in Italy, researchers found patients who had COVID were at higher risk of developing erectile dysfunction compared to men from the general population.

Doctors are taking all of these findings very seriously. Relatively recently, a group of urologists put out a PSA in honor of National Impotency Month and warned people to get vaccinated against COVID-19 in order to “save the future of boners,” citing evidence that the disease can cause erectile dysfunction in some patients. The internet was quick to label the syndrome with a catchy name: “COVID dick.” 

And although anecdotal, one man in his 30s claimed his penis shrunk by at least an inch while he was coping with the long-term side effects of COVID-19.

“I seemed to be left with a lasting problem. My penis has shrunk,” the man, who did not disclose his vaccine status, wrote. “It’s apparently due to vascular damage, and my doctors seem to think it’s likely permanent.” 

It is under the backdrop of concerning COVID side-effects some men suffer that researchers in Hong Kong purposefully infected male hamsters with various doses of SARS-COV-2, delivered intranasally. Some of the rodents were also vaccinated in order to examine if inoculation had any impact on testicular health.

The researchers found the sperm count and testosterone levels plummeted 4-7 days after the hamsters were infected with the virus. These effects may be a result of testicular damage. The testicles of the infected hamsters suffered from inflammation and even necrosis, which persisted for 120 days post-infection. The rodents that were vaccinated did not exhibit testicular damage, VICEreported.

Hamsters are often used in studies on viruses because their respiratory tract often reacts similarly to that of humans. However, these results still need to be treated with caution. The only way to tell if humans can also suffer testicular damage due to COVID is through randomized clinical trials.

“In summary, SARS-CoV-2 can cause acute and chronic testicular damage in hamsters and is consistent with the anecdotal reports of clinical orchitis and hypogonadism in recovered COVID-19 males. Long term follow-up of sperm count and sex hormone profile of convalescent COVID-19 males is
warranted,” the researchers wrote in their study.

The findings appeared in the journal Clinical Infectious Diseases.