Due to the “epidemic”, the Metropolitan Line was reopened after being forced to close on Saturday.
After being told by the app to self-quarantine in the morning, the staff controlling the roof could not go to work.
Since NHS Test and Trace has contacted staff, there is no service on the Metropolitan Line, which runs between Aldgate and Amersham in Buckinghamshire.
The Piccadilly and District lines were also affected, but they have also been reopened.
At the end of most restrictions in England on Monday, the government had received warnings that workers and medical personnel who had been forced to self-quarantine due to exposure to the coronavirus had “surged.
The transport union said that as the infection level rises, there will be “dire consequences” when workers are “warned” next week.
Railway, Maritime and Transportation Union (RMT) Secretary-General Mike Lynch had previously stated that Monday, “the number of workers receiving self-isolation orders next week will surge.”
“Even at this later stage, the government, train operators and bus companies should issue clear and legally supported instructions to bring the rest of the UK to the safety standards that are still valid in Wales and Scotland,” he said. .
In other parts of the country, as some frontline workers tested positive for Covid-19 or had to self-quarantine, passengers were warned this weekend that some northern routes will be changed.
