Plague Still Lingers: How Yersinia pestis Persists in Rodents and Fleas and What It Means for Public Health

Short Summary

Across centuries, plague has persisted not in humans alone but in the wild, cycling through rodent hosts and fleas. In this Science Friday segment, Flora Lichtman speaks with plague researcher Viveka Vadyvaloo about how Yersinia pestis established reservoirs after historic pandemics, the global hotspots where outbreaks occur, and how antibiotic access and vector control shape public health responses. The discussion clarifies why plague remains a present threat in poorer regions such as Madagascar and the DRC, how climate and environmental shifts could influence future transmission, and why eradication is unlikely but management is feasible. Listeners will learn how fleas, aging ecosystems, and social factors interact to drive occasional human cases and what people can do to reduce risk.

Introduction to Plague in the Modern World

The segment begins with Flora Lichtman introducing the paradox of plague, a disease often viewed as purely historical. Dr. Viveka Vadyvaloo explains that after medieval and Asian pandemics, the bacterium Yersinia pestis became established in rodent reservoirs worldwide, aided by increased global movement and trade. This conceptual shift frames plague as a disease of wildlife and fleas rather than just humans, with humans acting as incidental hosts when fleas seek new blood meals.

"The plague isn't just a medieval memory, it's a modern ecological story" - Dr. Viveka Vadyvaloo

Ecology and Transmission

The conversation details how plague cycles primarily between rodents and fleas, and how humans are typically bitten when an infected flea jumps to a person. Vadyvaloo emphasizes that plague ecology is well-studied in some regions, yet there remain knowledge gaps—especially around flea biology and its role in transmission. The interview highlights that plague is endemic on nearly every continent except Australia, with sentinel signs including rodent die-offs that trigger surveillance in places like the United States, China, Madagascar, and parts of Africa.

"Less is known about fleas than about ticks or mosquitoes, but they are critical to how plague spreads" - Dr. Viveka Vadyvaloo

Public Health Status and Treatment Access

The discussion turns to treatment and accessibility. Antibiotics can effectively treat plague, but access is uneven in resource-poor settings such as Madagascar and the DRC, where public health infrastructure may be limited. The host notes that human fatalities in the United States are relatively rare with early treatment, while Madagascar experiences seasonal outbreaks with higher case fatalities during outbreaks when healthcare access is constrained.

"Eradication is unlikely, but management and surveillance are feasible paths" - Dr. Viveka Vadyvaloo

Climate, Environment, and Future Risk

The interview considers climate and environmental drivers, noting that plague outbreaks often follow wet periods and heavy rainfall. Changes in climate could influence rodent and flea dynamics, potentially increasing the risk of human infections in endemic regions. The expert suggests that monitoring environmental signals and rodent population dynamics will be important components of public health planning as conditions shift.

"A wetter climate and heavy rainfall periods can signal outbreaks in endemic areas" - Dr. Viveka Vadyvaloo

Practical Takeaways for the Public

For the general public, the takeaway centers on practical prevention: minimize flea bites, be aware that pets can shuttle infected fleas into homes, and recognize plague symptoms that overlap with flu-like illness. The guest emphasizes ongoing surveillance and vector management as central to controlling outbreaks, while acknowledging resistance issues to chemical insecticides that call for safer, alternative strategies.

"People should be cautious in endemic areas and practice flea control and pet management to reduce risk" - Dr. Viveka Vadyvaloo