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Marmots, a type of rodent, can transmit the bubonic plague to humans

Reports of bubonic plague in Inner Mongolia earlier this week have attracted a significant amount of media attention.

With the emergence of COVID-19, the impact of infectious diseases on global public health has become a staple of everyday conversation. It’s understandable, then, that recent reports of bubonic plague in China have drawn the attention of the world’s media. But is there any cause for concern?

We spoke to Kelly Charniga of Imperial’s Department of Infectious Disease Epidemiology, whose research focusses on vector-borne diseases, about why the bubonic plague is not the next global public health crisis we need to worry about. 

Cases of bubonic plague are reported every year

“Worldwide, we tend to see between one to two thousand cases of plague per year, and most of these will be the bubonic form.”

“In the US, we expect about seven cases every year, which are mostly seen in the western part of the country – California, Colorado, New Mexico, Arizona. Most cases will appear in Africa – particularly Madagascar and the Democratic Republic of Congo – as well as Peru. Urban outbreaks are very uncommon, with most infections occurring in rural areas.”

Human-to-human transmission is rare

“There are three main types of plague, caused by the bacterium Yersinia pestis: bubonic, septicemic and pneumonic. Bubonic plague is the most common form and is spread by the bite of an infected flea. Humans can catch the disease in this way, or by coming into close contact with animals – typically rodents – who have been bitten and infected. This is also how septicemic plague is spread.”

“Pneumonic plague is usually characterised by symptoms of a lower respiratory tract infection – coughing, shortness of breath and fever. This is the most dangerous form of plague and the only type capable of human-to-human transmission, as it’s spread through respiratory droplets which can come out of an infected person’s mouth or nose when they cough, talk or sneeze.”

“The last major outbreak of plague occurred in Madagascar in 2017, affecting around 2,400 people in an urban area. This was the pneumonic form and a very unusual occurrence.”

It can be easily treated with antibiotics

“All forms of plague are easily treatable by antibiotics. It should be said that early diagnosis and treatment is important. Delaying treatment is one of the reasons why you tend to see higher mortality rates in developing countries where there may not be easy access to healthcare.”

There is nothing exceptional about the recently reported cases in China

“With infectious diseases, there are certain things that we keep an eye out for which may be a cause for concern. The first would be drug resistance: this is when infection-causing microorganisms adapt and change, developing resistance to traditional treatments like antibiotics. Although there was one multidrug-resistant strain isolated in Madagascar in 1995, this doesn’t appear to be an issue at the moment with any form of plague, including the most recently reported cases.”

“The other things we look for are unusually high numbers of cases, perhaps stemming from new forms of transmission, and cases being reported in new or unexpected locations. None of this is true of the recent cases in Inner Mongolia, where plague tends to occur occasionally.”

“The take-home message is that this isn’t something to worry about. COVID-19 is still the primary global health issue. It’s also important that we keep an eye on other infectious diseases right now, such as malaria, dengue, HIV and tuberculosis. All of these things are still affecting lots of people around the world, and COVID-19 has the potential to disrupt prevention activities and healthcare services for these conditions, leading to additional deaths.”