Plague

Online Q&A
October 2017

What is plague?

Plague is an infectious disease found in some small mammals and their fleas. People can contract plague if they are in bitten by infected fleas, and develop the bubonic form of plague. Sometimes bubonic plague progresses to pneumonic plague, when the bacteria reaches the lungs. Person-to-person transmission is possible through the inhalation of infected respiratory droplets of a person who has pneumonic plague. Common antibiotics are efficient to cure plague, if they are delivered very early, because the course of the disease is usually rapid.

What are the types of plague and how do people become infected?

There are two main forms of plague infection, depending on the route of infection: bubonic and pneumonic. All forms are treatable and curable if detected early enough.

  • Bubonic plague is the most common form of plague globally and is caused by the bite of an infected flea. Plague bacillus, Y. pestis, enters at the bite and travels through the lymphatic system to the nearest lymph node where it replicates itself. The lymph node then becomes inflamed, tense and painful, and is called a "bubo". At advanced stages of infection the inflamed lymph nodes can turn into open sores filled with puss. Human to human transmission of bubonic plague is rare. Bubonic plague can advance and spread to the lungs, which is the more severe type of plague called Pneumonic plague.

  • Pneumonic plague – or lung-based plague – is the most virulent form of plague. Incubation can be as short as 24 hours. Any person with pneumonic plague may transmit the disease via droplets to other humans. Untreated pneumonic plague, if not diagnosed and treated early, is fatal. However, recovery rates are high if detected and treated in time (within 24 hours of onset of symptoms).

What are the symptoms of plague?

Symptoms typically include sudden onset fever, chills, head and body aches and weakness, vomiting and nausea. Painful and inflamed lymph nodes can also appear during bubonic plague. Symptoms of the pneumonic form appear quickly after infection (sometimes less than 24 hours), and include severe respiratory symptoms such as shortness of breath and coughing, often with blood-tainted sputum.

How does pneumonic differ from bubonic plague?

Bubonic plague is the most common form of plague, but cannot be easily transmitted between people. Some people with bubonic plague will develop pneumonic plague, meaning the infection spreads to their lungs. Pneumonic plague can be transmitted between people through coughing. Bubonic plague has a mortality rate of 30% to 60%, while the pneumonic form is fatal in the absence of treatment. Both types have good recovery rates if people are treated in time.

How can I protect myself from being infected with plague?

To prevent the spread of pneumonic plague, avoid close contact (under 2 meters) with someone who is coughing, and reduce time spent in crowded areas. To prevent bubonic plague, do not touch dead animals and wear insect repellent while in plague endemic areas.

What should I do if I suspect I have plague?

In case of sudden symptoms of fever, chills, painful and inflamed lymph nodes, or shortness of breath with coughing and/or blood-tainted expectoration, people should immediately contact a medical provider for an evaluation. (Travellers who have left plague-affected areas should inform their health worker of their travel history to a plague-affected area.) People should avoid self-medication, including using antibiotics, unless they are diagnosed by a health worker.

How do you diagnose plague?

Health workers make an evaluation based on symptoms. Confirmation is based on laboratory testing from a sample of blood, sputum (fluid coughed up from inside the lungs) or pus from a bubo.

How can plague be treated?

Plague can be treated with antibiotics, and recovery is common if treatment starts early. In areas where there is a plague outbreak, people with symptoms should go to a health centre for evaluation and treatment. Patients with pneumonic plague must be isolated and treated by trained medical staff wearing personal protective equipment.

If I am in an area with an active plague outbreak, should I wear a mask to protect myself?

It depends on your level of exposure to sick people. People living in communities where there is a plague can wear masks if they wish, but masks must be used and disposed of properly so they do not become a source of infection themselves. Masks may help to reduce the spread of pneumonic plague if they are used correctly by people who are sick (to reduce the spread of droplets), and by health care workers (to protect themselves).

Do dead bodies spread plague?

The body of someone who has died after being infected with plague can infect people who are in close contact, such as those who are preparing the body for burial. The source of infection is the bacteria that are still present in body fluids.

More about plague