Transmission
How plague spreads: fleas, rodents and person-to-person transmission
Quick answer
- Plague is transmitted mainly by the bite of infected fleas, especially the rat flea (Xenopsylla cheopis).
- The natural cycle involves rodents and their fleas; contact with sick animals or carcasses can also transmit it.
- Person-to-person transmission occurs only in the pneumonic form, through respiratory droplets in close contact.
- Plague does not spread over distance through the air, nor through water or casual contact.
The cycle: rodent, flea and human
Plague circulates in nature in a cycle involving rodents and the fleas that live on them. When the bacterium reaches a rodent population, many animals become ill. Fleas that feed on an infected animal ingest the bacteria and can then transmit Yersinia pestis when they bite a person.
Why the flea is so efficient
The bacterium forms a blockage in the flea's digestive tract, causing it to attempt feeding repeatedly and regurgitate bacteria — increasing the chance of transmission.
Routes of transmission
| Route | Form | Note |
|---|---|---|
| Bite of an infected flea | Bubonic | Main transmission route |
| Contact with tissues/fluids of an infected animal | Bubonic, septicemic | Hunting, skinning, handling carcasses |
| Scratch/bite from a sick cat | Bubonic, pneumonic | Cats can transmit to humans |
| Respiratory droplets (person to person) | Pneumonic | Requires close, prolonged contact |
| Contaminated material in a laboratory | Any form | Rare; occupational accident |
Does plague pass from person to person?
Only pneumonic plague spreads between people, through respiratory droplets in close, prolonged contact. The bubonic and septicemic forms generally do not spread from person to person.
Droplets should not be confused with long-distance airborne transmission. Pneumonic plague does not spread through the air from room to room as efficiently as viruses such as measles.
How plague is NOT spread
- Not through the air over distance, unlike some respiratory viruses.
- Not through water or food, unless directly contaminated by an infected animal.
- Not through casual contact (handshakes, sharing a space without proximity).
- Not by mosquitoes — the vector is the flea.
Who is at higher risk
- People living or working where plague circulates among animals.
- Farm workers, hunters and those handling wildlife.
- People in homes with rodent infestation.
- Laboratory professionals handling the bacterium.
- Household contacts of pneumonic plague patients.
Frequently asked questions
Does plague pass from person to person?
Only in the pneumonic form, through respiratory droplets in close, prolonged contact. The bubonic and septicemic forms generally do not spread between people.
Is plague spread by mosquitoes?
No. The vector is the flea, mainly the rat flea (Xenopsylla cheopis).
Can I get plague by touching a sick animal?
Yes. Contact with tissues or fluids of infected animals, including handling carcasses, can transmit the bacterium. Use appropriate protection.
Does plague spread through the air?
Not over distance. The pneumonic form requires close, prolonged contact for droplet transmission. Plague does not behave like measles.
Sources
Medical review
Review by a licensed health professional is being arranged. This educational content is based on reference sources (WHO, CDC and medical literature) and does not replace evaluation, diagnosis or treatment by a health professional.
How this content was produced
- Who
- Produced by the Equipe editorial do Peste.com.br, the editorial team responsible for gathering, verifying and classifying public information about plague (Yersinia pestis).
- How
- Information is compiled from official and scientific sources (WHO, CDC and national health authorities) and from recognised news outlets. Every statement is classified as confirmed, reported or unconfirmed, and each article lists its sources.
- Why
- To offer clear, source-based information in Portuguese about plague and to separate verified fact from rumour. This content is educational and does not replace medical advice.
- Medical review
- Review by a licensed health professional is being arranged; no credential is claimed until a real professional is credited.
- Last review
See our sources and methodology and the editorial team.A revisão por profissional de saúde habilitado está em processo de credenciamento. Assim que concluída, o nome e o registro serão informados nesta página e nos dados estruturados.