Sweat may be another way to pass on hepatitis B infection during contact sports, suggests research published ahead of print in the British Journal of Sports Medicine.
Hepatitis B virus attacks the liver and can cause lifelong infection, cirrhosis (scarring) of the liver, liver cancer, liver failure, and death.
The research team analysed blood and sweat samples from 70 male Olympic wrestlers for evidence of hepatitis B infection (HBV).
The wrestlers, who were all aged between 18 and 30, were all asked about injuries, as blood-borne infection is a common route of transmission.
Over a third said they had had bleeding or weeping wounds during training and competition. And almost half said that they had had an episode of bleeding during other activities.
None of the wrestlers had active HBV infection, as evidenced by a lack of antibodies to the virus.
Nevertheless, the virus itself was found in the blood of nine (13%), suggesting that they had hidden or occult infection, says the author. This is perfectly plausible, given that intense training temporarily suppresses a normal immune response, she says.
Eight (11%) also had particles of the virus present in their sweat, and levels of the virus found in the blood closely matched those found in the sweat.
The findings prompt the author to suggest that sweat, like open wounds and mucous membranes, could be another way of transmitting the infection.
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, says the author.
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, she says, calling for HBV testing and vaccination for all wrestlers at the start of their career.