A researcher in Turkey says hepatitis B may be contracted by means of sweat during contact sports.
The researcher from Celar Bayar University in Izmir, reached this conclusion after examining blood and sweat samples from 70 male Olympic wrestlers for evidence of hepatitis B infection (HBV).
The Hepatitis B virus attacks the liver and causes a lifelong infection in approximately 5% of adults who catch it.
It can cause cirrhosis (scarring) of the liver, liver cancer, liver failure, and can be fatal.
The wrestlers, all between 18 and 30 years of age, were queried about injuries received during the sport as blood-borne infection is a common route of transmission.
Over a third of them said they frequently had bleeding or weeping wounds during training and competition and almost half said that they had had an episode of bleeding during other activities.
Although none of the wrestlers appeared to have an active HBV infection, the virus itself was found in the blood of nine (13%), which suggests says the researcher that they had a hidden or occult infection.
Study author Selda Bereket-Yucel says this is quite likely as intense training temporarily suppresses a normal immune response.
Another eight of the wrestlers (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.
Bereket-Yucel says the findings suggest that sweat, like open wounds and mucous membranes, could be another way of transmitting the infection.
However some experts say that catching it through sweat, rather than blood, remains extremely unlikely as while a single drop of blood can hold millions of viable viruses it is unclear whether the viral particles found in sweat could infect someone and the risk is quite low.
The biggest risks of catching the virus are generally thought to be through unprotected sex and through infected blood.
The author points out that 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, despite the fact that HBV is far more transmissible, because far higher levels of the virus are found in the blood and it is more robust than HIV.
Bereket-Yucel has called for HBV testing and vaccination to be mandatory for all wrestlers at the start of their career as sweating could be another way of transmitting the HBV infection in contact sports.
The study is published in the British Journal of Sports Medicine.