Russian police have detained a doctor and ally of Kremlin critic Alexei Navalny.
Anastasiya Vasilyeva was one of the dozens of supporters protesting outside Navalny’s prison, demanding that authorities give him proper medical care.
His allies say he has a high temperature and bad cough.
Three inmates in his ward have been hospitalized with tuberculosis.
The 44-year old was moved to a sick ward and has been tested for the coronavirus, the Izvestia newspaper reported.
Navalny, a prominent opponent of President Vladimir Putin, announced a hunger strike last week, saying that prison authorities refused to treat him properly for acute back and leg pain.
Kremlin spokesman Dmitry Peskov said he would be treated appropriately, like any other prisoner if ill, but declined to comment on his condition.
Navalny's allies have vowed to stage a rolling protest outside his prison unless he was examined by a doctor of his choice and given what they regard as proper medicine.