Adnkronos (Adnkronos) – From history books to today's headlines. Plague, back in the spotlight with the death of 28-year-old Daria Chipilova, a laboratory researcher at the Irkutsk Anti-Plague Institute, is a disease with ancient origins, yet it has never completely disappeared from the world's radar, evoking a collective image of devastation.
It was not by chance known as the "Black Death" in the 3th century, when it caused over 50 million deaths in Europe, nearly a third of the population that inhabited this area at the time—in 1350. And in Europe, the disease remained endemic, returning in 10-12 year cycles for at least the next three centuries, according to the Epicentro portal of the Italian National Institute of Health (ISS).
Today, however, plague numbers are no longer comparable to those of the past, it is curable with antibiotics (those commonly used for enterobacteria), and early diagnosis and treatment are the key to saving human lives.
But of the three forms of the disease, the pulmonary one that is suspected to have affected the young scientist in Siberia is the most virulent.
It occurs when the zoonotic bacterium Yersinia pestis – which normally hosts parasitic fleas of rodents, rats, some species of squirrels, prairie dogs, and sometimes even domestic animals such as cats – infects the lungs, but can also result from the degeneration of other forms (bubonic and septicemic) if not treated promptly.
The incubation period can be as short as 24 hours (for other forms, it can be up to 7), the World Health Organization notes in a focus article. And anyone infected can transmit the disease to other humans through respiratory particles, i.e., through the air or infected aerosols. For this reason, as the ISS's Epicentro portal explains, it is considered one of the most dangerous forms due to its inherent epidemic potential. This is also the reason behind the measures implemented following the case detected in Siberia (with 200 people under observation and anti-contagion measures in place). The chances of recovery for this form also increase if the disease is treated promptly. However, if not diagnosed and treated early, it can be fatal in 100% of cases (in the most common form, bubonic plague, mortality can range from 30 to 60%). Along with septicemic plague, the pneumonic form is therefore among the most serious, but fortunately less common.
As for symptoms, while bubonic plague includes sudden-onset fever, chills, headache, muscle aches, weakness, vomiting, and nausea, and may also cause painful and swollen lymph nodes, the pneumonic form includes severe respiratory symptoms that appear very quickly (sometimes in less than 24 hours), ranging from shortness of breath to a cough, often with blood-tinged sputum. There is little data on the pneumonic form of plague alone, but in July of last year, for example, an alert came from the United States, where Arizona reported its first pneumonic plague death since 2007, in a man who had professional contact with sick cats. Two days after the patient's death, preliminary diagnostic test results confirmed the suspicion of pneumonic plague, leading to the immediate identification of potentially exposed individuals and their treatment with post-exposure prophylaxis, as explained by the CDC (Centers for Disease Control and Prevention).
Overall, considering all forms, the most recent figures from the World Health Organization (WHO) indicate that between 2019 and 2025, 3.860 suspected cases were reported, of which 2.646 were confirmed from 10 countries (mainly the Democratic Republic of the Congo, Kenya, Madagascar, Uganda, China, and Mongolia, and to a lesser extent in Brazil, Qatar, and Saudi Arabia). Deaths in the six most affected countries totaled 423, corresponding to a case fatality rate of 11%. The DRC and Madagascar combined account for 97,7% of confirmed cases.
In areas where plague is endemic, preliminary diagnostic test results, combined with clinical suspicion of pneumonic plague, can lead to timely public health interventions, the CDC emphasizes, recommending that healthcare workers in these areas consider the disease in patients with severe respiratory and systemic manifestations who have been exposed to sick animals. Appropriate laboratory safety practices should also be evaluated for clinical laboratory personnel handling specimens from these patients. "The risk of pneumonic plague increases with occupational exposure to Y. pestis-infected animals, particularly cats, due to their susceptibility to plague," the US agency highlights. "When evaluating sick animals and people suspected of having plague or handling their clinical specimens, consistent use of personal protective equipment, particularly adequate respiratory protection, can reduce occupational exposure to zoonotic pathogens such as plague among veterinary, medical, and clinical microbiology personnel."
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