Health officials say the disease, which contributed to the deaths of more than 50 million people in Europe during the Middle Ages, has spread from rural areas into urban areas not usually affected.
Hundreds of cases are reported on the tropical island every year, but experts are warning the epidemic is “much more dangerous” than in previous years.
Officials have reported infections in 17 of huge island nation’s 22 regions since the outbreak started in August.
Popular tourist destination Madagascar usually sees between 300 and 600 cases of plague annually, but this year’s epidemic has infected more than 900.
A total of 97 people are confirmed to have died from the disease so far.
The bubonic strain of the disease is spread through the bites of infected fleas, whereas the more contagious pneumonic type is spread through coughing – and experts say the infectious strain is quickly spreading in to towns.
Elhadj As Sy, secretary general of the International Federation of Red Cross and Red Crescent Societies, told Thomson Reuters: “The number of cases is growing by the day.”
He said overcoming the epidemic would require long-term help, not “just intervening at the peak and then forgetting about it”.
Plague can be treated with antibiotics and is not usually fatal when people seek treatment.
But Mr Sy added he was concerned the stigma surrounding the disease could “drive people underground” and spread the illness further.
He said: ”Our volunteers are working in communities convincing people to seek help.”
Medical staff from the Red Cross are in the country to help deal with the outbreak and are reportedly using careful burial practices which avoid contact with corpses.
Dr Manitra Rakotoarivony, Madagascar’s director of health promotion, said: “Normally, people who catch the plague live in poor areas, but people in every place in society are catching the disease.”
Jimmy Whitworth, professor of International Public Health at the London School of Hygiene and Tropical Medicine, told the Sun: “It has been a long time since we have seen the plague in an urban environment.
“The risk of it spreading internationally is low.
“But the risk of this continuing to spread within Madagascar is still quite high.”