Researchers from universities in Germany and Iran have found lower sperm counts and motility, as well as evidence of testicular damage, in studies conducted on men who contracted Covid-19.

Scientists at the Justus-Liebig-University in Germany and Allameh Tabataba’i University in Iran have identified significant inflammation markers in samples of testicular tissue from 84 Covid-19 patients.

When compared to a control group, inflammation and cellular stress in the Covid-19 positive patients was twice as severe, with sperm motility three times slower and sperm counts significantly lower.

“These effects on sperm cells are associated with lower sperm quality and reduced fertility potential,” noted lead researcher Behzad Hajizadeh Maleki.

“Although these effects tended to improve over time, they remained significantly and abnormally higher in the Covid-19 patients, and the magnitude of these changes were also related to disease severity,” Maleki further warned.

A recent review of studies conducted by the Open Biology journal also warned that the virus poses a “global threat to male fertility potential.”

Researchers at the Sheba Medical Centre in Tel Aviv, Israel also reported finding a 50% reduction in sperm motility, concentration and volume in patients who had experienced moderate Covid-19 symptoms 30 days before.

A 2020 Miami University study found the virus can enter testicle tissues and damage sperm.

The Lancet estimates that global fertility will fall below 1.7 by 2100, with 2.1 children per woman being the figure needed for population replacement.

CNN previously reported on studies estimating that sperm counts in North America, Europe, Australia and New Zealand have dropped by almost 60% in 38 years between 1973 and 2011.

Male testosterone has also exhibited a similar decline, with western diets thought to be a significant contributing factor in the changes.