Bath's Heineken Champions Cup fixture with La Rochelle on Saturday has been cancelled due to Covid-19 outbreaks.
Bath lost a Pool A opener to Scarlets, who have had a positive test confirmed, and 12 Bath players are now isolating.
Bath also confirmed one positive test from an injured player "not currently in training" and "one further player was identified as a close contact".
Exeter's Heineken Champions Cup match at Toulouse and Glasgow Warriors against Lyon has also been postponed.
"Due to the impact on selection availability of forwards, it is not possible to safely fulfil the fixture on Saturday," a Bath statement explained.
As per its Covid-19 protocol, European Professional Club Rugby will convene a Match Result Resolution Committee to determine the result of the game.
Stuart Hooper, Bath's director of rugby, said: "We are hugely disappointed that we are unable to play this fixture, but the health and safety of our staff, players and families - and that of La Rochelle's rugby community must be our top priority.
"Our focus now is to continue to protect our people and to prepare for our upcoming fixture against London Irish on Boxing Day."