With the discovery of 13 skeletons in London that are believed to be victims of the ‘Black Death’ plague and a new study suggesting that the plague continues to pose risks, the infectious disease is back in the spotlight.

Scientists are hoping that the 13 skeletons, discovered Friday by workers digging a new rail line, will shed light on the DNA properties of the disease.

“It’s a very important find of reasonably well preserved skeletal material. It means we can go forward from here, we can do years of research looking into the microbiology, the DNA of the disease,” said Don Walker, of the Museum of London.

Meanwhile a new study published Friday in the journal Infection, Genetics and Evolution said innovation in transportation technology and the emergence of antibiotic-resistant strains of Yersinia pestis – the disease-causing bacteria-- “is raising serious concerns for public health.”

It may surprise many that the plague, which at its height is estimated to have killed between 75 and 200 million people worldwide during the 14th century, still poses health risks today.

Yet the disease afflicts between one and 17 people in the U.S. each year, according to the U.S. Centers for Disease Control and Prevention.

Human plague remains low in Canada, with the last recorded case dating back to 1939, according the Public Health Agency of Canada.

Here are some facts about the plague:

What is it?

The plague is an infectious disease that is found rodents and other small animals. It is caused by the Yersinia pestis bacteria, which is found around the world including in the U.S. and Canada.

There are three forms of the plague: bubonic, septicemic and pneumonic. The bubonic plague infects the lymph nodes, the septicemic plague infects the blood and the pneumonic plague infects the lungs.

The bubonic plague is the most common type of plague and is usually caused by infected flea bites.

Pneumonic plague is the least common type of plague and is typically caused by inhaling infected droplets from an individual who has the plague, or when a case of bubonic or septicemic plague is left untreated and then spreads to the lungs.

Pneumonic plague is the most serious form of the disease. Patients who have the pneumonic plague can die 24 hours after infection.

Septicemic plague occurs with either the bubonic or pneumonic plague.

How does it spread to humans?

The plague can spread to humans through flea bites, contact with infected tissue or through the spread of infectious droplets that contain the Yersinia pestis bacteria.

The plague can spread from human to human when an infected individual has pneumonic plague and spreads cough droplets containing the plague bacteria into the air.

What are the symptoms of the plague?

Symptoms of plague can include: fever, headaches, vomiting, diarrhea, chills and swollen and painful lymph nodes.

In cases of septicemic plague, a patient’s skin may turn black around the fingers, toes and the nose.

Patients who have pneumonic plague may experience shortness of breath, chest pain and bloody or watery mucous.

Can the plague be treated?

The plague can be treated with antibiotics. With a quick diagnosis and rapid treatment, most cases can be cured.

The mortality rate of the plague in the U.S. is around 11 per cent. The WHO says global mortality rate is around eight to 10 per cent.

Recently there have been concerns that anti-biotic resistant strains of the plague may be emerging in some developing countries.

How common is the plague?

The Center for Disease Control estimates that there are between one and seventeen human plague cases each year in the U.S., with 80 per cent of them being bubonic cases.

The World Health Organization estimates that between 1,000 and 2,000 cases of plague are reported each year.

Who is at risk for the plague?

The risk of plague is highest in rural and semi-rural areas, particularly in areas that house and shelter rodents. In North America, human plague is most prevalent in the southwestern U.S.

Globally, human plague is prevalent in parts of central, eastern and southern Africa, Asia and South America.

With files from The Center for Disease Control and The Public Health Agency of Canada