CLINICAL MATTERS
The Russian government earlier this month reported the death of a 28-year-old laboratory researcher in Serbia from pneumonia. The researcher worked in the Irkutsk Research Anti-Plague Institute, and so naturally people were alarmed that she may have been infected by the plague bacteria that she was working on. Several co-workers have been quarantined even as Russian authorities sought to downplay any link between plague and the researcher’s pneumonia diagnosis.
Pneumonia can be caused by many kinds of bacteria and viruses. Some of these can be deadly even for a young 28-year-old, and we do not know if she had any underlying illnesses that would increase the risk of contracting pneumonia. At this time, there is no evidence that what the researcher had is pneumonic plague. The World Health Organization (WHO) and the US Centers for Disease Control (CDC) are understandably trying to obtain more information, and it remains to be seen if Russia will release the full results of its investigation.
What is plague, and can it cause pneumonia? What is the likelihood that this is what the researcher contracted? How probable is it that this will make it to the Philippines? Should we be worried or is this a false alarm?
Plague is caused by the bacterium Yersinia pestis. It is usually transmitted to humans from the bite of the rat flea. It can also be transmitted from close contact with infected animals. There are several forms of plague: bubonic plague, septicemic plague, and pneumonic plague. The most common form is bubonic plague which predominantly affects the lymphatic system. Bubonic plague can be deadly, especially if it progresses to septicemic or pneumonic plague. Pneumonic plague is specific to the lungs and can be acquired by the inhalation of respiratory droplets from infected animals or humans. Septicemic and pneumonic plague is deadlier bubonic plague and can reach 100 percent fatality without treatment.
Yersinia pestis is found throughout the world, including the Philippines. Historical archives reveal bubonic plague outbreaks in the Philippines. A paper from the Journal of the American Medical Association from 1913 reported 55 cases of bubonic plague in Manila. 46 Filipinos, eight Chinese, and one Caucasian were infected. All cases were handled in San Lazaro Hospital.
While the infamous “Black Death” killed up to 200 million people in the Middle Ages, plague is no longer as deadly. The availability of effective antibiotics, improved diagnostics and modern hygienic practices make plague outbreaks more manageable. Sporadic cases from natural infection involving wild or feral animals do still occur, including a recent pneumonic plague case in the United States in 2025.
Antibiotics used for the treatment of plague include fluoroquinolones (ciprofloxacin and levofloxacin), aminoglycosides and tetracyclines. Prompt diagnosis is essential and if treatment is started within 24 hours of symptom onset, there is a good chance of survival. While bubonic plague is not transmitted from person to person, pneumonic plague can be contagious. Contact tracing and quarantine should be initiated if this is suspected and close contacts offered antibiotic prophylaxis. A vaccine against plague exists but is not available locally.
Because of its inherent deadliness, plague is historically one of the diseases that have been weaponized. The Soviet Union and the United States had active programs to weaponize plague from the 1960s, until production was banned in the 1970s. Used as an aerosol, it can infect a significant number of people with pneumonic plague. Russia may possibly still have some leftover plague stocks from the Soviet Union, and this is why the US CDC and WHO are concerned about the recent pneumonia case and have called for greater transparency.
At the time of this writing, Russia has denied that plague is involved and has already evaluated most of the case’s close contacts. Even if this is found to be pneumonic plague, WHO has assessed the overall public health risk as low. It is working with Russian authorities to prevent any future potential exposures. In the meantime, it doesn’t hurt to be vigilant especially for those people in the vulnerable population. Consult only high-quality information sources for the latest updates. Don’t fall for fake news which, in a way, is a plague of its own.
