IPM Take
The most dangerous misunderstanding about plague is not that it has returned. It is that it ever disappeared.
Modern antibiotics make plague treatable when recognised promptly, but the bacterium remains established in animal reservoirs and flea populations. WHO’s seven-year review shows a disease that is geographically concentrated, unevenly reported and still capable of producing fatal outbreaks when surveillance and treatment arrive late.
Executive Summary
WHO’s review of human plague between 2019 and 2025 identified 3,860 suspected cases reported by 10 countries.
Six countries reported confirmed infections: the Democratic Republic of the Congo, Madagascar, Kenya, Uganda, China and Mongolia. Across those six countries, 2,646 confirmed cases were reported. The DRC and Madagascar together accounted for 97.7% of confirmed cases.
WHO also recorded 423 deaths among 3,847 suspected cases reported by those six countries, corresponding to an 11% case-fatality proportion among suspected cases. Reporting was incomplete, and WHO cautions that absence of submitted data should not be interpreted as absence of plague.
Why it matters
- Public authorities: Surveillance has to extend beyond human cases into animal hosts, fleas and environmental conditions capable of signalling increased risk earlier.
- Clinicians: Rapid recognition matters because plague can be effectively treated with antibiotics, while delayed diagnosis substantially worsens outcomes.
- Global surveillance systems: Missing country data can create false reassurance precisely where zoonotic reservoirs remain established.
Few infectious diseases carry as much historical baggage as plague. That can distort modern risk in two opposite directions. The name creates an image of medieval catastrophe, encouraging sensationalism when a case appears, while the assumption that plague belongs to another era makes persistent transmission easier to overlook.
WHO’s latest global review offers a more useful picture. Plague remains geographically limited but biologically entrenched. Thousands of suspected infections were reported between 2019 and 2025, with confirmed disease overwhelmingly concentrated in the Democratic Republic of the Congo and Madagascar. Smaller numbers occurred elsewhere, reflecting natural foci in which Yersinia pestis circulates among animal reservoirs and flea vectors.
That ecology changes what elimination means. Unlike an infection maintained only through human transmission, plague can persist outside the human population. Preventing human disease therefore requires more than finding people once they become sick. Animal surveillance, flea monitoring and environmental intelligence can provide warning before human cases expose the problem.
This is One Health in unusually literal form. Rodent populations, flea density, rainfall, land use, human housing and access to healthcare can all affect whether an enzootic infection becomes a clinical emergency. Health ministries that see plague exclusively through hospital reporting are looking at the final stage of a much longer biological chain.
The WHO data also contain an important warning about what surveillance cannot conclude. Ten countries provided information on suspected cases during the seven-year period, but reporting was not comprehensive. Countries with recognised plague foci were among those for which WHO did not receive data for the period. No report should therefore be translated into no transmission.
That distinction matters for resource allocation. Rare diseases are vulnerable to a circular policy failure: limited surveillance produces few confirmed cases; few confirmed cases reduce political interest; lower political interest further weakens surveillance. The resulting absence of data can then be mistaken for evidence that the investment is unnecessary.
Urban pneumonic plague remains the scenario that makes preparedness particularly important. Pneumonic disease can spread between people through respiratory droplets during close contact and progresses rapidly without treatment. Large urban outbreaks are uncommon, but Madagascar’s 2017 experience demonstrated why authorities cannot assume that plague will remain confined to remote rural settings.
The appropriate response is not fear. It is competence. Antibiotics are effective when disease is diagnosed and treated early. Laboratories can confirm infection. Epidemiological teams can investigate contacts. Vector and animal surveillance can identify increased risk.
The modern plague challenge is therefore not a lack of tools. It is keeping those tools operational for a disease whose rarity makes complacency politically attractive.
Plague has not returned from history.
It never left the ecology.
