Elisah Raharimalala and her daughter wear face masks as they make their way around the capital of Madagascar, Antananarivo, a city of more than a million people. They're wearing the mouth and nose coverings to protect themselves not from air pollution or the common cold but from the plague, a disease that in the West is more commonly associated with the Middle Ages.

"We are worried because we live in the less-pleasant part of the town," said Raharimalala. "Our place is clean, but in the communities around us, there are dead rats."

In 14th-century Europe, the plague was known as the Black Death and by some estimates caused an estimated 50 million deaths during that period.

In Canada, there has not been a human case of the plague since 1939 (although a case was detected in a Saskatchewan prairie dog this summer). Worldwide, there are between 1,000 and 2,000 reported cases a year, largely confined to rural areas, according to the Centers for Disease Control and Prevention.

But now, a deadly outbreak of plague is spreading across Madagascar, a country that already had the highest number of cases of the disease in the world.

And it's spreading fast — faster than it has in the past in Madagascar, according to the World Health Organization (WHO).

"People just don't think of plague in 2017 as a cause of illness. We think of this in medieval times killing a huge proportion of the world but lo and behold, it's alive and well," said Dr.Isaac Bogoch, an infectious disease and tropical medicine specialist at the Toronto General Hospital.

"This is not something like Ebola or Zika where we are worried about this spreading all over the world. Plague is already in many, many parts of the world, but cases are usually very sporadic, and there are limited amount of cases per year. Madagascar just seems to be a hotbed and has been for some time."

A disease of poverty

WHO spokesperson Tarik Jasarevic explained that Madagascar sees more cases of plague than other poor countries because of several factors that combine to create just the right conditions for the spread of the disease: plague is already present on the island; rats live in close proximity to humans; and people live in poverty with unsanitary living conditions.

Madagascar’s government has launched a public awareness campaign informing people about the recent outbreak and urging them to take precautions against fleas and rats by practicing good hygiene. (Annie Burns-Pieper/CBC)

"Plague is first a disease of small mammals, and human transmission is accidental," Jasarevic said. "The risk of human transmission depends on several factors, namely, the nature of the animal reservoir [of infection] and the conditions of living."

The most common form of plague, the bubonic plague, is a bacterial infection spread to humans through infected fleas that have contracted the infection from small animals they've bitten, such as rats, or through direct contact with infected tissue or inhalation of infected droplets.

If left untreated, the bacteria can spread through the bloodstream to the lungs, which causes the pneumonic form of the plague. This can then be passed from person to person through coughing.

The government has temporarily closed the country's schools to prevent the spread of the plague and disinfect buildings and is monitoring the whereabouts of those infected. (Annie Burns-Pieper/CBC)

The infection causes flu-like symptoms and can be treated with antibiotics if caught in time but can be fatal if not treated early.

Both bubonic and pneumonic forms of the plague are currently present in Madagascar.

The WHO calls the plague a disease of poverty because it thrives in places with unsanitary conditions and inadequate health care. Madagascar is one of the poorest countries in the world. UNICEF estimates around 82 per cent of the population of 25 million lives below the international poverty line, meaning they live on less than $1.90 US a day.

'Start of the epidemic season'

"Infections like this are much more problematic in developing countries with limited public health capacity," said Bogoch. "If people cannot access medical care quickly, they are more likely to spread the disease without knowing it. In Madagascar, many people live in remote areas without easy access to medical care."

Between 2010 and 2015, Madagascar accounted for about 82 per cent of the deaths from plague worldwide. Out of a total 584 reported deaths, 476 were in Madagascar.

Since late August, the country has had 162 reported cases of plague and 30 reported deaths. Madagascar sees cases of plague every year, but the difference this year is it is affecting highly populated areas, which has led the disease to spread more quickly than in the past.

Sambatra Razafindramanana, 17, on the streets of Antananarivo, where pharmacies are running out of face masks as people grow increasingly anxious about the spread of the plague. 'I am afraid that I'll be contaminated. Tana is a red zone now, according to the news,' she said using the common shorthand for Antananarivo. (Annie Burns-Piieper/CBC)

"Contrary to past outbreaks, this one is affecting large urban areas and port cities, which increases the risk of person-to-person transmission," he said.

In Antananarivo, one of the people killed by plague was a basketball coach from the Seychelles who died while visiting the capital for a basketball tournament. Nine other people have died from the plague in the city, and 16 others were hospitalized.

"WHO is concerned that plague could spread further because it is already present in several cities, and this is the start of the epidemic season, which usually runs from September to April," said Dr. Charlotte Ndiaye, the WHO representative in Madagascar.

Urban pulmonary plague 'most frightening'

Madagascar's minister of public health, Mamy Lalatiana Andriamanarivo, said the government is particularly worried about the disease spreading in urban areas.

"What makes this plague different from the case before is the existence of urban pulmonary plague," said Andriamanarivo.

"Urban pulmonary plague can be transmitted by saliva. It spreads very quickly. It's most frightening because it can reach many people."

Priscilla Rasamoely is a pharmacist in Antananarivo. The pharmacy she works at has sold out of face masks.

Speaking to reporters, Madagascar's public health minister, Mamy Lalatiana Andriamanarivo, said the government is particularly worried about the disease spreading in urban areas. (Annie Burns-Pieper/CBC)

Rasamoely says she has been advised by the country's order of pharmacists to reassure the public, and she's been busy in the last few days talking to people concerned about the disease.

"We give them advice about the plague and hygiene," she said. "They should not self-medicate. We teach them the hygiene to fight against fleas and rats. Those in contact with sick people should wear a mask if there is a high fever."

The government is tracking where individuals who have been infected live, where they have gone and who they have come into contact with and says they are working night and day to treat those who have contracted the illness.

There is epidemiological monitoring of people coming in and leaving the country in place at the airport in Antananarivo.

The Public Health Agency of Canada has updated the travel health notice for Madagascar on the travel.gc.ca website but is not advising against travel to the country. The agency said it is also "communicating with travel health professionals to recommend that they provide travelers to Madagascar with appropriate health advice."

Schools in Madagascar are temporarily closed to prevent the spread of the plague and to give the government a chance to disinfect buildings.

The government is also planning public awareness campaigns on TV and radio and is providing new training for doctors and paramedics on treating the plague and dealing with those infected.

The WHO says it has deployed more staff to Madagascar, released $300,000 in emergency funds and provided medical supplies in response to the outbreak.

But Benjamin Andriamintantsoa, an opposition member of the National Assembly, says lifting the country out of poverty would help prevent outbreaks like the one the country is experiencing.

"We are are in the 21st century, and in Madagascar, there is plague, because of the poverty. People are poor, and they are fighting to survive," he said.