COVID-19 may negatively affect sperm quality and reduce fertility in men, according to German research. The study of 84 men with confirmed COVID-19 and 105 healthy controls found that in men with COVID-19, markers of inflammation and oxidative stress in sperm cells were significantly increased by more than 100 per cent. The pathways that facilitate sperm cell death were also activated, and sperm concentration was reduced by 516 per cent, mobility by 209 per cent and sperm cell shape was altered by 400 per cent. The authors say these effects on sperm cells are associated with lower sperm quality and reduced fertility potential. 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.