Scientists have claimed Coronavirus may lead to infertility in men even if they only suffer a mild form of the disease.
Sperm counts of infected men halved 30 days after they were diagnosed with Covid-19, according to a study.
And researchers in Israel, where it was conducted, also claim sperm motility — or its ability to move by itself — was also hampered.
But scientists insist the truth on whether Covid-19 permanently damages fertility is still murky, and that even flu causes a temporary drop in sperm counts.
The research was published in the journal of Fertility and Sterility, according to the Jerusalem Post, which reported the changes were seen in men with mild cases.
But the journal has yet to publicly release the paper, meaning top scientists from around the world have yet to be able to point out obvious flaws in its method.
Scientists studying the effect of coronavirus on fertility have, however, made similar claims in the past.
But doctors insist reports of men having lower sperm counts are likely down to them having had a fever — a tell-tale symptom of coronavirus.
This, scientists say, makes it harder for the body to produce sperm. They also argue that production can bounce back after an infection has passed.
When Mailonline reached Professor Allan Pacey, an andrologist at the University of Sheffield and former chair of the British Fertility Society, he said he wouldn’t be surprised if coronavirus caused a temporary drop in sperm production.
But the jury is still out on whether or not the effect could be long-lasting, harming the fertility of men.
‘People who get coronavirus are probably quite unwell, even influenza will cause a decline in sperm count temporarily,’ he said.
‘The question is whether it is permanent and whether it is recoverable.’
Research is yet to reveal whether long-term damage can be caused to testicles by coronavirus, and it could take several years before scientists have the answer.
Previous research has indicated, however, that any damage caused to the testes by an infection is not long-term.
Professor Pacey cautioned against the finding in the new Israeli research that coronavirus can damage cells in the testicles responsible for making semen and the male hormone testosterone.
The doctors claimed that was the case after examining 12 men who had died from the virus. The Jerusalem Post did not expand on this observation in any greater clarity.
But Professor Pacey pointed out deceased patients would have been much sicker than the average infected man, and are likely to have been older, which would also cause a drop in the amount of sperm they produce.
‘There’s a bit of caution there because if you’re in ICU and you die you’re very sick, so we shouldn’t be surprised if there are changes in the testicles,’ he said. ‘Also, men who get very sick and are in ICU tend to be older.’
He also poured cold water on the finding that 13 per cent of sperm samples taken of infected men contained the virus, as reported by the Jerusalem Post.
‘I think that’s very difficult to prove and I’d like to read the paper,’ he said.
‘We’ve done work on other viruses, for example chlamydia, a bacteria that behaves like a virus, and it’s really difficult to prove if the virus is inside the sperm.’
It is unclear whether the virus could be transmitted through this route, but there is no evidence that it can be passed via semen or vaginal fluids.
The virus, scientifically called SARS-CoV-2, could be passed through kissing during sex, however.
Dr Dan Aderka, from the Sheba Medical Center, who carried out the study, claimed that coronavirus could harm the testicles by binding to the ACE2 receptors on their cells.
These receptors, which act as a gateway for the virus to enter cells, are the same as those on the lungs, heart and intestines.
But scientists have previously pointed out that to do this the coronavirus would need to enter the bloodstream, and there’s no ‘clear mechanism’ for it to do this.
Professor Ian Jones, a virologist at the University of Reading, told MailOnline in April that coronaviruses do not generally travel in the blood.
‘The main site of virus replication is the respiratory tract,’ he said. ‘(Travel in the bloodstream) has been reported for the virus but it is not generally what coronaviruses do.’
Professor Pacey said he can’t see a mechanism whereby coronavirus would become blood-borne. ‘I may be wrong, this is a new virus, we’re learning all the time,’ he said.