A new research revealed that sweat may be another way to transmit the hepatitis B infection during contact sports. Hepatitis B is a disease of the liver provoked by the Hepatite B virus (HBV).

This virus has caused current epidemics in parts of Asia (like China) and Africa and 3-6 % of the world population is infected with the virus, although up to 35 % have been exposed.

HBV provokes lifelong infection of the liver, cirrhosis (fibrotic tissue replacing the normal tissue) of the liver, liver cancer, liver failure, and death.

The research team used blood and sweat samples from 70 male Olympic wrestlers, all aged 18 to 30, to look for evidence of HBV infection. The wrestlers were all interviewed about injuries, as blood-borne infection is a common route of transmission of HBV and not only. More than a third declared they had bled or got wounds during training and competition. About a half stated that they had experienced bleeding provoked by other activities, outside sports life.

The analysis of the blood detected no presence of antibodies against the HBV, thus none of the wrestlers had active HBV infection. "Nevertheless, the virus itself was found in the blood of nine (13%), suggesting that they had hidden or occult infection. This is perfectly plausible, given that intense training temporarily suppresses a normal immune response," said the authors.

Eight (11%) subjects also presented virus components in their sweat; in fact, the sweat presented the same virus level as the one found in the blood. This discovery made the authors point that sweat, like open wounds and mucous membranes, is another way the virus transmits itself from one individual to another.

"Some sporting bodies have ruled that HIV testing should be mandatory for all contact sport competitors, but no such recommendations have been made for HBV. Yet HBV is far more transmissible, because much higher levels of the virus are found in the blood and it is not as fragile as HIV, calling for HBV testing and vaccination for all wrestlers at the start of their career."