All five remain in stable condition, with illness described as mild to moderate, the hospital told RIA Novosti. Fontanka first reported the confirmed diagnoses.
News that five people had been admitted with suspected infection emerged late last week. The hospital's press service said at the time that none of them were seriously ill.
According to the city health committee, the patients were placed in a new building on Piskaryovsky Prospekt that was designed in part to handle especially dangerous infections.
The Telegram channel Mash reported that four of the patients were taken from a single apartment in the Krasnogvardeysky district and that all of them had presumably been in contact with the source of the infection. No official statement has been made on where the virus came from.
The regional branch of Rospotrebnadzor, the federal consumer protection and public health agency, said it was identifying people who had been in contact with the patients and issued an order to carry out disinfection.
On October 18, epidemiologist and Russian Academy of Sciences academician Gennady Onishchenko told TASS that the situation "should not lead to a serious spread of the infection." The registered cases will be treated, he said.
Monkeypox is a viral disease that, in addition to fever and general intoxication, produces a characteristic rash on the skin. The infection spreads from person to person or from infected animals through close physical contact. According to TV Rain, the fatality rate ranges from 1% to 10% depending on the strain of the virus.