Sources & methods

Explainers

Plague explained

The science behind the news: what plague is, how it spreads, and how outbreaks are contained.

Plague

Plague bacteria under a fluorescence microscope

Plague5 min read · Checked 11 Oct 2026Pneumonic plaguePneumonic plague is plague in the lungs and, CDC says, the only form that spreads between people. What WHO and CDC say about symptoms, spread and treatment.

Oriental rat flea (Xenopsylla cheopis) infected with plague bacteria, seen under a microscope

Plague6 min read · Checked 11 Oct 2026Pneumonic vs bubonic plaguePneumonic vs bubonic plague: bubonic infects lymph nodes, usually after a flea bite; pneumonic infects the lungs and can spread between people by droplets.

Plague bacteria under a fluorescence microscope

PlaguePneumonic plague5 min read · Checked 11 Oct 2026

Oriental rat flea (Xenopsylla cheopis) infected with plague bacteria, seen under a microscope

PlaguePneumonic vs bubonic plague6 min read · Checked 11 Oct 2026

Spread

Spread5 min read · Checked 11 Oct 2026How diseases spreadDiseases spread by a few modes of transmission: contact, surfaces, droplets, air, vectors, food and water, and mother to child. Each one explained, with plague.

Spread7 min read · Checked 11 Oct 2026Airborne vs dropletAirborne vs droplet: droplets are larger particles that fall within a short distance; airborne particles stay in the air and travel farther. Where plague fits.Spread6 min read · Checked 11 Oct 2026Incubation periodAn incubation period is the time from infection to first symptoms. See how it differs from the latent period and what WHO and CDC say about plague's range.Spread6 min read · Checked 11 Oct 2026R0 and the reproduction numberR0, or R naught, is the basic reproduction number: how many people one case infects on average. How it differs from Rt, why it varies, and plague estimates.

SpreadHow diseases spread5 min read · Checked 11 Oct 2026

SpreadAirborne vs droplet7 min read · Checked 11 Oct 2026 SpreadIncubation period6 min read · Checked 11 Oct 2026 SpreadR0 and the reproduction number6 min read · Checked 11 Oct 2026

Control

Two N95 respirators resting on a table, one teal and one white

Control6 min read · Checked 11 Oct 2026Transmission-based precautionsTransmission-based precautions are the contact, droplet and airborne measures hospitals add to standard precautions. CDC lists pneumonic plague under droplet.

Laboratory worker in a gown, respirator and gloves at a biosafety cabinet

Control6 min read · Checked 11 Oct 2026Isolation vs quarantineIsolation separates people who are sick; quarantine restricts exposed people who are not yet sick. How long each lasts, what WHO and CDC say, and why 40 days.Control6 min read · Checked 11 Oct 2026Contact tracingContact tracing finds people exposed to an infection, tells them, and watches them for one incubation period. See the steps and who counts as a close contact.

Two N95 respirators resting on a table, one teal and one white

ControlTransmission-based precautions6 min read · Checked 11 Oct 2026

Laboratory worker in a gown, respirator and gloves at a biosafety cabinet

ControlIsolation vs quarantine6 min read · Checked 11 Oct 2026 ControlContact tracing6 min read · Checked 11 Oct 2026