Pneumonic Plague: Symptoms, Causes, and Treatment

If you talk about the plague, images of the Middle Ages with unsanitary conditions, countless rats and many deserted regions inevitably come to mind. After all, the plague epidemics in the Middle Ages claimed over 20 million lives. But even today, according to the WHO, the plague bacteria kill 1,000-3,000 people every year – most recently, the pneumonic plague that broke out in northwest China.

Plague – what is it?

The plague is a bacterial disease that can take very different courses: In the worst case, it leads to death as pneumonic plague within a few days; the harmless variant leads to a mild flu-like reaction in the body with some fever and malaise (an abortive form of plague). The plague bacteria can be transmitted to humans through the bite of an infected flea or passed from person to person as a droplet infection, for example, when coughing.

How common are plague diseases, and where do they occur?

While Europe and Australia are considered plague-free, there are areas in Asia, Africa and America where regional plague outbreaks occur repeatedly. People with a lot of direct contact with animals are particularly at risk: hunters, veterinarians, shepherds, or other people who live in close quarters with their animals. Infected fleas can spread especially under poor hygienic conditions and in areas with a low standard of living, where many people – and animals – live together in a confined space, infecting humans, rats and other rodents. Although the conditions for the global spread of a focus of infection are not given as in the Middle Ages, there are local outbreaks of plague every year, sometimes killing several hundred or even thousands. Uganda, Congo, India and China have been affected in recent years – but even in the southwest of the USA, there are occasional plague infections among cat owners whose animals catch diseased prairie dogs.

Bubonic plague, pneumonic plague – what’s the difference?

The same pathogen causes the different forms of plague. In the case of bubonic plague, painful swelling of the lymph nodes occurs locally at the site of the bite – the lymph nodes and ducts can form bulges up to 10 centimetres thick (hence the name). On the other hand, the plague sufferer shows a high fever, flu symptoms, and possibly unconsciousness. Bubonic plague often turns into plague sepsis ( sepsis = blood poisoning), in which the bacteria spread with the blood to all organs, leading to disease symptoms. While bubonic plague is fatal in about half of all diseases, plague sepsis is almost always fatal without targeted antibiotic treatment – after just 1 to 2 days.

The clinical picture of pneumonic plague is similarly fatal. There, too, up to 95% of all those infected die within a few days – probably because the body’s defence system can fight the infection too late due to the direct contact of the pathogens with the lungs. Those affected cough develop bloody sputum after a short time and lung failure with shortness of breath and blood backlog to the heart. Sometimes, the plague also begins with a sore throat, which, like bubonic plague, can degenerate into plague sepsis if left untreated. Only the abortive plague is a harmless variant accompanied by mild cold symptoms. If you survive an attack of plague, you have lifelong immunity against this dangerous disease.

What can you do if you get sick with the plague?

If plague is suspected, rapidly administering antibiotic substances such as streptomycin, tetracycline, or doxycycline is usually life-saving – this can reduce mortality to less than 20%. Detecting the pathogen in the blood secures the diagnosis, but because of the dramatic course of the disease, treatment is usually started before a result is available. 

In addition, destroying infected fleas using insecticides and the control of rodents in the affected area are of particular importance. These measures prevent other people from becoming infected with the plague pathogens.

How can you prevent a plague outbreak?

Protections against flea bites in areas known for plague outbreaks, such as covering the legs and modern insect repellents, are a matter of course for people staying in at-risk areas, as is keeping rodents away. If you have encountered the pathogens, administering antibiotics over several days is recommended. Although there is a vaccine against the plague pathogen, it is only of limited effectiveness and poorly tolerated.