Plague explained
Information only, not medical advice. Source: WHO plague fact sheet and the US CDC.
What it is
Plague is a bacterial disease caused by Yersinia pestis. It mainly affects wild rodents and their fleas, and can pass to people.
The three forms
- Bubonic is the most common form. It follows a flea bite or contact with infected animal tissue and causes swollen, painful lymph nodes. It does not spread easily between people.
- Septicaemic plague is infection of the blood, and can follow bubonic plague or arise directly.
- Pneumonic plague affects the lungs. It is the most serious form and the only one that can spread person to person through respiratory droplets, usually after close, prolonged contact with a sick person.
Treatment and prevention
- Plague is treatable with common antibiotics when started early. Delay greatly increases the risk of death, especially in the pneumonic form.
- Contacts of a pneumonic case are usually given preventive antibiotics and monitored. Quarantine of contacts is a standard precaution and does not by itself mean spread has occurred.
- There is no widely available licensed vaccine for the general public.
Why it is not a pandemic risk today
Plague still occurs in parts of Africa, Asia and the Americas each year, in small numbers. Modern antibiotics, hygiene and rodent control make large outbreaks unlikely.