What is plague Cause of the plague?

A plague is a zoonotic infection caused by the bacterium Yersinia pestis, transmitted by fleas. Although the times of epidemics are over, it is still suffered in some countries. Knowing how to identify and prevent it will avoid greater evils.

Fever is a disease caused by bacteria ( Yersinia pestis ) that can carry rodents and other mammals. Flea bites usually transmit it. Humanity has suffered extensive plagues with great mortality in the past, including the 14th century Black Death which depleted a third of Europe’s population. The last plague pandemic with millions affected worldwide was more than 100 years ago.

Plague is a severe pathology that initially resembles the flu but rapidly evolves into the bubonic form (with the appearance of large swollen and very painful lymph nodes), pneumonia (with severe pneumonia with very high mortality without treatment and even with it), or septicemic.

Although antibiotics are available for the treatment of plague, diagnosis is often delayed if the disease is not suspected, and even with early treatment, mortality is high.

The diagnosis of plague is made by visualizing and culturing the bacteria in samples taken from the patient or by serology. Treatment should not be delayed until confirmation is obtained but should be started immediately in a person with a compatible clinic who has been in an area where plague is present in the local fauna, especially in cases where there is a flea bite.

Currently, there are cases of plague in parts of Africa and some specific cases in the United States of America. In South America, there is only an isolated focus in Peru and Brazil. In Western Europe, there have been no cases of plague in recent decades, and the last case in Spain dates from 1932. In Mongolia, a case of bubonic plague infection was detected in a herder in July 2020.

Causes of plague

The plague is an infection caused by the bacterium Yersinia pestis. It is a type of gram-negative coccobacillus from the group of Enterobacteriaceae that grows inside cells. This bacteria can infect rodents, prairie marmots, squirrels, camels, and occasionally household pets. They are what is known as the reservoir of bacteria. Animals become infected by eating meat from an infected animal and by the bite of fleas that carry yersinia.

Humans can be infected by this bacterium mainly through flea bites from infected animals or through bites or scratches. Other ways of transmitting plague are handling infected animal tissues and the inhalation of respiratory secretions from animals or humans with the pneumonic form of the infection. Carrying out an autopsy on an infected person or handling laboratory samples is another possible route of transmission.

Plague is a disease that can be found in fauna almost everywhere globally (except Australia), although currently, most human cases occur in poor or developing countries. It is mainly associated with environments with poor hygiene and poor living conditions.

There have been three major plague epidemics: in the 6th century, the 14th century – the Black Death, which killed about 50 million people worldwide, half in Europe – and the late 19th century. It was in this latest epidemic that the bacteria was discovered.

Currently, the Yersinia pestis affects animals in North America and the former Soviet Union, and there are some pockets in parts of Africa, Asia, and South America. Since 2000, more than 95% of cases have occurred in Africa, the most affected countries being Madagascar and the Democratic Republic of the Congo.

Much alarm has been generated in the US in recent times by some specific cases of plague, but in reality, this disease has not been eradicated in this country, and every year, there are some cases. 

For example, in 2006, there were 17 cases (2 fatal), and in 2014, 10 cases (none fatal). Most occur in parts of the American West. There have been no cases of plague in Europe since the early 20th century. In South America, there have been some in Peru (one in 2015). There are currently no records of plague in Western Europe.