Recently, concerns have been raised by reports that COVID-19 could be transmitted sexually, based on its presence in semen by RT-PCR. However, caution must be exercised in drawing any conclusions about sexual transmissibility, based on the above.
It's instructive that the original SARS virus uses the same ACE2 receptor as COVID-19, and in 20 years since it first affected humans, not a single case of sexual transmission (based on epidemiologic or molecular studies) has been described for SARS.
The question we need to ask ourselves is therefore, whether presence of a virus in semen equates with sexual transmission. Fortunately, in Medicine, when you think of a query, somebody else has considered it before and tried to answer it. The paper below from the United Kingdom- "Breadth of Viruses in Human Semen"- did just that in 2017, in the wake of the Zika virus outbreak. Apart from SARS, they documented 26 other viruses that appear in the human semen. Of these, less than half have ever had known sexual transmission. The list includes viruses you would never think of being passed on sexually, such as Chicken pox, Mumps and Chikungunya.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5652425/
If one is observant, one will notice some glaring omissions in that list. Where's HPV, for example, that well known scourge of teenagers, the purveyor of genital warts, vulval and cervical cancer? Well, it's transmitted sexually, just not through semen. Presence in semen therefore does not equate with sexual transmission. Nor does the absence of a virus in semen provide reassurance that it is not transmitted sexually.
NEJM even ran an editorial on this in 2018- "Virus in Semen and the Risk of Sexual Transmission"-and I quote, "Contrary to prevalent belief, the detection of viral genomes in semen tends to be more common among viruses that are typically not sexually transmitted, such as certain adenoviruses, bunyaviruses, flaviviruses, hepadnaviruses, herpesviruses, paramyxoviruses, and retroviruses"
https://www.nejm.org/doi/full/10.1056/NEJMe1803212
There is another important issue- these COVID-19 virus particles found in semen may not be replication competent. RT-PCR only signifies the presence of the bit of the viral RNA that PCR probe primes with. It will do so regardless of whether the virus has a capsid or not- ie "live" or "dead".
It's instructive that the original SARS virus uses the same ACE2 receptor as COVID-19, and in 20 years since it first affected humans, not a single case of sexual transmission (based on epidemiologic or molecular studies) has been described for SARS.
The question we need to ask ourselves is therefore, whether presence of a virus in semen equates with sexual transmission. Fortunately, in Medicine, when you think of a query, somebody else has considered it before and tried to answer it. The paper below from the United Kingdom- "Breadth of Viruses in Human Semen"- did just that in 2017, in the wake of the Zika virus outbreak. Apart from SARS, they documented 26 other viruses that appear in the human semen. Of these, less than half have ever had known sexual transmission. The list includes viruses you would never think of being passed on sexually, such as Chicken pox, Mumps and Chikungunya.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5652425/
If one is observant, one will notice some glaring omissions in that list. Where's HPV, for example, that well known scourge of teenagers, the purveyor of genital warts, vulval and cervical cancer? Well, it's transmitted sexually, just not through semen. Presence in semen therefore does not equate with sexual transmission. Nor does the absence of a virus in semen provide reassurance that it is not transmitted sexually.
NEJM even ran an editorial on this in 2018- "Virus in Semen and the Risk of Sexual Transmission"-and I quote, "Contrary to prevalent belief, the detection of viral genomes in semen tends to be more common among viruses that are typically not sexually transmitted, such as certain adenoviruses, bunyaviruses, flaviviruses, hepadnaviruses, herpesviruses, paramyxoviruses, and retroviruses"
https://www.nejm.org/doi/full/10.1056/NEJMe1803212
There is another important issue- these COVID-19 virus particles found in semen may not be replication competent. RT-PCR only signifies the presence of the bit of the viral RNA that PCR probe primes with. It will do so regardless of whether the virus has a capsid or not- ie "live" or "dead".
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