A pilot of study in India has identified a possible reason why men suffer worse effects when infected with the novel coronavirus - and it may reveal a painful truth for men.
The study, which tracked the clearance of the virus from patients in Mumbai, focused on the body's angiotensin converting enzyme 2 (ACE2) cells.
These receptors bind to the coronavirus and are found in large amounts in the lungs, heart and gut in both men and women.
All of those areas have been found to be vulnerable to 2019-nCoV, the virus that causes Covid-19.
One area of the male body also produces ACE2 cells at a high rate: the testes.
Ovaries do not.
The study found that in the female patients, the median time to clear the virus from the body was four days.
In the men, the median was six days.
The study described the testes as "testicular viral reservoirs" and suggested they could be responsible for the slower rate of clearance.
• Covid 19: Coronavirus can spread through soles of shoes, study reveals
• Covid 19 coronavirus: Online learning 'game-changing' - but many may still miss out
• Covid 19 coronavirus: Why it's too tempting to believe the Oxford study on coronavirus
• Covid 19 coronavirus: Virus able to survive in 60C temperatures
Co-author of the study, Dr Aditi Shastri, told the Los Angeles Times that if the coronavirus is found in the testes, that might mean the virus can be sexually transmitted.
"I would definitely consider that virus could be secreted into seminal fluid," she said.
Dr Kathryn Sandberg of Georgetown University, who studies gender differences in immune response, told the Los Angles Times that women are known to fight viruses better than men, partly because their immune systems have a stronger initial response to exposure.
Sandberg said the theory that coronavirus could be idle in the testes is "speculative".
But she added that "it's worth pointing out to people who have forgotten that ACE2 is in the testes, and could be a player".