Coronavirus transmission through semen cannot be completely ruled out, a top fertility expert has warned.
Professor Allan Pacey, an andrologist at the University of Sheffield, said there was ‘currently little evidence’ of the virus being passed on via the bodily fluid.
But the theory can’t be discarded because research on the topic is extremely limited, according to the former chairman of the British Fertility Society.
There has been some analysis which ‘suggests Covid might be present in the testicles’, which makes transmission via semen possible, he said.
Professor Pacey claims to have reviewed the 14 best scientific papers on Covid-19 and male fertility published so far.
Only four of the studies involved a control group – critical in robust and unbiased research – and which in total only covered a small sample of men, less than 300.
Professor Pacey told the virtual Progress Educational Trust conference on fertility, genomics and Covid-19 today: ‘There is little current evidence that Sars-Cov-2 [the virus that causes Covid-19] is transmitted in semen.
‘But I don’t think I can completely rule it out, so we still need to carry on with further studies.’
Coronavirus transmission through semen cannot be completely ruled out, a top fertility expert has warned (file)
Covid-19 uses its infamous spike protein to bind to ACE2 proteins and invade human cells.
The receptor is found most commonly in the respiratory tract, but also on the heart, blood vessels, kidneys, liver – and in the testicles.
Dr Richard Viney, a consultant urological surgeon in Birmingham, told MailOnline in April: ‘The testicle is known to express the ACE2 receptor that the virus uses to access cells so this could explain why the testicles might be a target for Covid-19.’
Professor Pacey said he found very little evidence so far that getting coronavirus affects male fertility in the long-term.
He added: ‘I think there was a plausible reason to be concerned about fertility issues in men affected by Sars CoV-2.
‘But the initial data does not really support the hypothesis that either reproductive hormones or sperm quality are affected.’
He said there was some emerging evidence that the virus lingered in the testicles without causing damage, which happens with other viruses including Ebola, Zika and dengue.
‘The testes is an immuno-privilege site and viruses can, kind of, hang around there for quite some time without causing any clinical pathology to the individual,’ he said.
One study, which is yet to be peer-reviewed, involved a small group of men who were admitted to a hospital in China with Covid-19 and tested positive for the virus in their semen.
There have been other small studies suggesting that sperm counts of Covid-19 infected men temporarily declined after they were diagnosed with the disease.
But Professor Pacey said studies such as these have caveats and should not be seen as conclusive as they ‘looked at a remarkably small number of men’.
Meanwhile, Ashley Moffett, emeritus professor of reproductive immunology at the University of Cambridge, who was also speaking at the conference, said that there is no evidence that pregnant women are more seriously at risk of death from Covid-19 infection.
But she added that, at the moment, it is too early to recommend Covid-19 vaccines for mothers-to-be until more data becomes available.
Professor Moffett said: ‘The vaccine trials did not include pregnant women so this will have to wait until we have that information.’
Scientists are also unsure whether testicular pain could be a rare sign of Covid.
Through the pandemic there have been several cases of Covid-positive men with the symptom around the world.
One small study in China suggested it was as common as one in five.
The most recent case study, reported last month, involved a 49-year-old man in Turkey, who sought medical advice because of swelling and pain in the left side of his groin and testicles in the summer.
He did not have any symptoms of the coronavirus, such as a persistent cough or high temperature.
However, doctors decided to swab him for the disease because he was in contact with someone who had later tested positive.
Results showed he had coronavirus, therefore the doctors suspected the testicular pain was his first symptom. They said he didn’t have any other health problems that could have caused it, such as an STI.
The tale was revealed in the medical journal Urology Case Reports by doctors at Acıbadem Mehmet Ali Aydinlar University in Istanbul, Turkey.