Squalid, overcrowded and prone to deadly riots, Brazil's prisons now face a new problem as COVID-19 spreads inside them, pushing already precarious health services to the brink and increasing inmates' isolation from their families.
From the dingy, poorly ventilated cells to the limited rations of food and water to the violence to the overcrowding, which can reach up to four times capacity, Brazil's prisons were already bleak places before the coronavirus pandemic engulfed the country.
Now, for both inmates and their families, the virus has made the ordeal of incarceration even worse.
"I'm afraid of losing my husband inside. There's never been adequate medical care, and now the worry is even worse because we're dealing with an invisible enemy," said one Sao Paulo inmate's wife, who asked her name not be used.
Brazil has the third-biggest prison population in the world after the United States and China, with nearly 750,000 inmates -- well over the official capacity of 440,000.
The South American country also has the second-highest number of infections and deaths in the pandemic, after the US: more than 3.5 million and 112,000, respectively.
Since the first case of COVID-19 was confirmed in a Rio de Janeiro prison in April, the virus has spread quickly through Brazil's jails, despite the suspension of visits and transfers.
More than 17,300 inmates have been infected and nearly 100 have died, according to the National Penitentiary Department.
But experts say the real numbers are probably much higher. Just 7.8 percent of inmates have been tested.
"We have no idea what the real situation is," said Alexandra Sanchez, a researcher at Brazil's leading public health institute, Fiocruz.
"Inmates' health was already a major problem. Now, with COVID-19, we don't know what's going to happen."
In a recent, comprehensive study in the Sao Paulo prison Sorocaba II, 38 percent of the 2,095 inmates tested positive for the virus.
That is around 13 percentage points higher than even the worst-affected slums in Rio de Janeiro, Sanchez said.
"That's an extremely high rate. The spread of the virus is stunning," she told AFP.
A paper she recently co-authored warns of the impact the pandemic is having on prisoners.
"Inmates' fears for their lives and health, combined with restrictions on movement within the prisons and the interruption of work, educational and religious activities, are aggravating tensions, with serious emotional implications for the prison population," it said.
- 'Mom, I'm sick' -
Another inmate's relative shared a letter from her 29-year-old son, incarcerated for drug crimes and sharing a cell with 41 other prisoners in Sao Paulo.
"Mom, I'm sick. Several of us have symptoms, and the infirmary isn't doing anything," it said.
"It's an agonizing situation. There is information they aren't sharing with us.... But we know things aren't good," said the woman.
The authorities suspended all prison visits in March in hopes of containing the virus, and at minimum-security prisons revoked inmates' right to leave during the day for work.
That sparked prison riots and mass escape attempts. More riots followed, over fears that guards would bring the virus inside.
The preventive measures did not stop the virus, likely transmitted by employees in many cases.
Of the 110,000 employees in the prison system, 7,143 have been infected with the virus and 75 have died, according to the National Justice Council (CNJ), a public watchdog.
The Inter-American Commission on Human Rights voiced concern this month over the rapid spread of the virus in Brazil's prisons, and called on the authorities to reduce overcrowding and grant parol whenever possible.
"We are seeing an increase in violations of prisoners' human rights during the pandemic," said Leonardo Biagioni de Lima, of the Sao Paulo public defender's office.
His team found during an inspection of the Sorocaba II prison that inmates with confirmed and probable cases of COVID-19 were sharing cells with apparently uninfected prisoners.
De Lima called the prison authorities' response "very timid."
The justice ministry says it has released 49,747 prisoners during the pandemic, following a recommendation from the CNJ to grant parol to non-violent offenders.
But experts say the number could be much higher, including around 2,000 pregnant or nursing mothers.