Pneumonic plague: Symptoms, transmission risks and global monitoring

A researcher at the Irkutsk Plague Research Institute in Siberia has died, prompting quarantine measures for several individuals. The Russian consumer protection agency, Rospotrebnadzor, downplayed any link between the death and her work at the institute. However, the incident raised questions about potential infection with pneumonic plague, considered the most dangerous form of the illness.

The situation has drawn attention in the United States, where the State Department and the Centers for Disease Control and Prevention stated they are closely monitoring developments. The World Health Organization confirmed it is in contact with Russian health authorities to verify the circumstances of the death and ongoing tests, while assessing any potential international public health implications.

What defines pneumonic plague?

Pneumonic plague is a rare and severe lung infection caused by the bacterium Yersinia pestis. Scientists regard it as the most lethal variant of the disease. It differs from bubonic plague, the most common form, which typically spreads through flea bites or bacterial entry via skin wounds, causing painful lymph node swelling. Untreated, bubonic plague can progress to septicemic plague affecting the bloodstream. Pharyngeal plague infects the throat after consuming meat from infected animals.

How does transmission occur?

Pneumonic plague is the only form that transmits directly between humans via respiratory droplets from coughing or sneezing. Infection can also spread through droplets from affected animals. The last documented person-to-person transmission in the United States occurred in 1924 during an outbreak in Los Angeles.

The bacteria settle in the lungs, causing acute pneumonia and breathing difficulties. Symptoms may appear within 24 hours of infection. These include fever, chills, headache, body aches, dizziness, weakness, fatigue, nausea, vomiting, and diarrhea. Without treatment, the disease is fatal in most cases.

Treatment and prevention protocols

Antibiotics treat plague effectively, requiring a course of at least 10 to 14 days. Common medications include ciprofloxacin, levofloxacin, moxifloxacin, gentamicin, and streptomycin. Survival chances improve significantly if treatment begins within the first 24 hours. Patients may also need supportive care involving oxygen, fluids, and rest.

Although vaccines have existed since the 19th century, the WHO does not recommend general vaccination. It is reserved for high-risk groups, such as laboratory workers who frequently handle the pathogen.

Why does the plague persist?

Historically linked to the Black Death, which killed over 50 million people in Europe during the 14th century, the plague remains present today. While antibiotics have made treatment more effective, the disease persists on all continents except Oceania. Since the 1990s, the majority of human cases have been recorded in Africa, according to WHO data.