The Premier League club had said on Sunday one of their players had tested positive following a second batch of testing but did not disclose his identity.
"My test last Monday before we started training was negative," Ramsdale told the Sun. "So this last week, I've done the usual things like going to the supermarket and going to the petrol station to fill my car up.
"I've been just as careful as before on lockdown and it seems to be a shopping trip where I've caught it."
Ramsdale had returned to training when the Premier League allowed clubs to conduct sessions in small groups with players adhering to social distancing guidelines.
The 22-year-old said he did not have any symptoms and that he was now self-isolating.
"Now I have seven days' isolation at home ... It's not ideal, obviously, with training.
"The club have been fantastic. The players and especially the staff have been saying if we need anything to just ask. Things like shopping, they'll leave it at the door."
The club said on Sunday their training facilities were still safe environments.
"Following strict adherence of the Premier League's return to training regulations, the club's training ground remains a safe working environment for players and backroom staff, who will continue to be tested for COVID-19 twice per week," they said.