Twelve inmates in a single ward at Iran's notorious Evin prison have contracted Covid-19, according to the wife of one of the inmates.
Seventeen people on ward eight at the jail in Tehran were tested for coronavirus even though more than that number were showing symptoms, according to Monir Abdi, whose husband was one of those affected.
The 12 who tested positive were moved to two separate rooms at the prison's clinic but only one has since been transferred to hospital, she told the rights group Centre for Human Rights in Iran.
"By keeping political prisoners in overcrowded and unsanitary prisons where they are denied medical care and are not separated from ill prisoners, the Iranian authorities are condemning these individuals to Covid-19 and possible death," Hadi Ghaemi, the group's executive director, said.
Those affected include Ms Abdi's husband, Esmail Abdi, who was jailed for six years after organising peaceful protests against the detention of trade unionists and poor wages in the education sector. Lawyer Amirsalar Davouudi, who was sentenced to more than 29 years in prison for his human rights work was also stricken, according to the rights group.
It called on the Iranian authorities to release all prisoners testing positive for Covid-19, those displaying symptoms and those who came into contact with people who were infected.
"Coronavirus complications started to appear among the prisoners in ward eight two weeks ago," Ms Abdi told the group.
"The symptoms began two weeks ago, including loss of the sense of smell and taste, heartburn and severe coughing.
"In the prison clinic the infected prisoners have not been given any particular medications. Only their temperature is being monitored."
She said her husband had a pre-existing medical condition and had been prescribed blood pressure medicine. "He has become very weak and we are very worried about his food intake," she said.
"We want him to be granted furlough or be taken to the hospital. We prefer furlough because the hospitals are full. It's a dangerous situation. Let him come home; we will keep him in quarantine and take care of him."
The Free Workers Union of Iran, which campaigns for better wages for employees, said its chairman had also been infected.
Iran's political prisoners were largely left out of the mass release of inmates in March, which was designed to slow the mounting death toll. Some 100,000 prisoners were given temporary freedom from Iran's overcrowded jails and many have since returned, including Mr Abdi.
His wife said that inmates were initially given some face masks and items to improve hygiene but had since been left to fend for themselves and forced to buy overpriced items from the prison shop.
United Nations human rights experts in April called for the release of all political and foreign prisoners in Iran to avert the serious risk of infection from Covid-19.
A British-Iranian dual citizen, Anoosheh Ashoori told The National in April how disease prevention measures had been undermined by incompetent staff.