Experts warned of an epidemic of the bubonic plague in Madagascar if authorities don't work to slow its spread.
The plague, which notoriously ravaged Europe in the 14th century, spreads through fleas and is on the rise on the island in the Indian Ocean.
The 'Black Death' killed an estimated 25 million people in medieval Europe, but is now considered rare.
The situation in Madagascar has not escalated to that level, but there are worrying signs.
The plague spikes in October in the southern hemisphere as hot, humid weather begins. Last year, Madagascar recorded 256 cases of the disease with 60 dead.
That figure could rise even higher this year, experts believe.
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The Red Cross and the Pasteur Institute said that the country's jails are particularly at risk due to the number of rats and fleas.
"If the plague gets into prisons there could be a sort of atomic explosion of plague within the town. The prison walls will never prevent the plague from getting out and invading the rest of the town," said the Pasteur institute's Christophe Rogier, according to BBC.
"Rat control is essential for preventing the plague, because rodents spread the bacillus to fleas that can then infect humans," said Christoph Vogt, head of the Red Cross delegation in Madagascar. "So the relatives of a detainee can pick up the disease on a visit to the prison. And a released detainee returning to his community without having been treated can also spread the disease."
The disease itself can be treated with antibiotics if caught early.
Madagascar and the Democratic Republic of Congo reportedly contain 90 percent of cases of the plague in recent years.