A case of bubonic plague has been diagnosed in the U.S. Here's what Canadians should know

An empty hospital bed is shown. (Timothy Huliselan / Pexels.com)

Once known as a harbinger of death that caused widespread outbreaks, the plague has become an infectious disease that can be treated with antibiotics if diagnosed early.

In a recent U.S. case, a sick pet cat was believed to be the source of bubonic plague – the most common form of the plague – in Oregon this week.

Although public health officials believe people in the community are not at risk, the infected resident in Oregon, the cat and the resident's close contacts were treated with medication, The Associated Press reported. The cat died.

The plague is a bacterial infection that affects about 20 countries around the world, said Isaac Bogoch, a Toronto-based infectious disease specialist.

Bogoch said there's an "extremely low risk" of contracting the plague in Canada.

"When someone mentioned the plague you think back to the 1300s where this infection killed a third of Europe, but of course it's not doing that these days," he said in a Zoom interview with CTVNews.ca on Wednesday. "There are periodic outbreaks from time to time in certain parts of the world. ... It might be forgotten but it's not gone."

More than 50 million people died from the plague, known as the "Black Death," in Asia, Africa and Europe during the 14th century.

"It can occur in rodent populations in Canada so it's something that certainly could very, very, very rarely but theoretically could jump from non-human animals to humans in Canada," Bogoch said. "It would just be a very unusual event."

Where plague is found

Though still uncommon, an average of seven human plague cases have been reported each year in recent decades in the U.S. and human-to-human transmission hasn't been confirmed in the U.S. since 1925, according to the Public Health Agency of Canada (PHAC) and the U.S. Centers for Disease Control and Prevention (CDC). From 2010 to 2015, 3,248 human cases were reported globally, including 584 deaths, according to the World Health Organization.

Most human cases have occurred in Africa since the 1990s, with "epidemic recurrences" in Madagascar, PHAC said.

"It is possible that plague is more common in Africa as poor rural communities live in close proximity to rodents," PHAC wrote on its website. "Rodents are widely hunted and eaten in plague-endemic areas."

Bogoch said Madagascar and the Democratic Republic of Congo are the two countries with the most cases of plague. In Madagascar, cases typically occur between September and April, with an occasional larger outbreak such as in 2017.

"There are opportunities for what we call 'zoonotic spread,' meaning the transmission of infections from non-human animals to humans. More interactions with animals that have the potential to be infected by plague may mean more human cases," he explained in an email. "But in general, this is an extraordinarily rare infection in North America."

Cases in Canada

In Canada, human cases are "very rare," according to PHAC.

"Official reporting of human plague cases by local public health started in 1930, with the first case being reported in 1939, said PHAC spokesperson Anna Maddison in an email to CTVNews.ca on Wednesday. "Since then there have been no known cases of human plague in Canada."

Maddison said she could not immediately provide further details, including whether Canada is currently monitoring the situation.

"We sometimes get information about plague in wild animals and pets," PHAC wrote on its website. "This information comes from research studies, animal health authorities or Parks Canada."

How does the plague spread?

The plague is spread in various ways from infected animals and humans.

An infected flea can spread it through a bite, according to PHAC. Direct contact with the infected tissues or fluids of an infected animal or human, such as with your nose, mouth or broken skin, can result in contracting the disease.

Breathing in droplets from the coughs or sneezes of an infected individual can also transmit the plague.

Symptoms: What is the plague?

Bogoch said the plague is transmitted between fleas and rodents in a "flea-rodent cycle."

"Yersinia pestis is the bacteria that causes plague, a clinical syndrome that is very serious in humans," he said.

The plague has other forms such as bubonic plague, septicemic plague and pneumonic plague, according to PHAC.

The most common form is bubonic plague. "That's where you get a big, swollen painful lymph node, usually it's in the groin and people can get pretty sick from this," Bogoch said, noting that the "bubo" (meaning "groin" in Greek) is the big swollen lymph node at the groin.

For bubonic plague, symptoms typically include weakness, fever and chills, head and body aches. Swollen and painful lymph nodes are usually found near where the bacteria entered the human body.

For septicemic plague, infection spreads through the blood and causes symptoms like bleeding and shock, according to PHAC. It may also cause fever and make the skin turn black, particularly on the toes, fingers and nose and it's usually a complication of bubonic plague, PHAC noted.

Pneumonic plague is the most serious and less common form of the disease. Symptoms include coughing, chest pain, high fever, weakness, shortness of breath, bloody or watery mucus, and pneumonia. In this case, the lung is infected and it's the only form of plague that can be transmitted between humans through air droplets, PHAC said. People can get infected through the cough or sneeze of an infected person or animal and from untreated bubonic or septicemic plague.

Risks of getting disease

Anyone who lives close to infected animals or fleas faces a risk of contracting the plague, according to PHAC. The plague is found in small animals, such as rats, ground squirrels and other rodents, and their fleas.

It can affect anyone of all ages and genders. Most cases occur among people living in small towns, villages or agricultural areas.

Before travelling, people are advised to check if the plague is endemic in their destination. Travellers are at risk if they are camping, hunting or near rodents, PHAC said.

However, it added that the risk of international travellers getting infected is "low."

Treatments

Bogoch said people will get sick enough to seek care if they get the plague. To prevent it, he advises people to not handle dead or sick animals or wildlife.

He said the disease is easily treatable. "There are several antibiotics that are rather conventional and readily available in Canada that work just fine," he explained.

But he warned that the disease could worsen if a person doesn't seek care immediately.

"In countries where plague is endemic, if people have delays in antibiotics, the probability of more severe illness and death is higher," Bogoch said. "If people present to care early and rapidly start antimicrobial treatment then the probability of recovery is much higher."

According to PHAC, the plague "can be severe." The bubonic plague has a case fatality rate of 40-70 per cent and is "almost always fatal" for the pneumonic and septicemic forms if left untreated, it said on its website.

"Early diagnosis and treatment are essential due to the rapid course of the disease," PHAC said.

With files from The Associated Press