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What is Plague and How do People get it?


Plague disease is a severe illness that can result in pneumonia, swollen glands, blood infection, and death. It is caused by bacteria named Yersinia pestis.


Plague killed millions in the 14th century and was called the Black Death. In 1900, there was an outbreak of plague in San Francisco caused by infected rats brought by a ship. Plague is mainly a disease of rodents and is most common in the southwestern United States, particularly Arizona and New Mexico. Naturally occurring plague causes an average of 5 to 15 human cases each year in the western United States. From 1994-2006, eight cases of plague were reported in California; none of these cases were in San Francisco.


People can touch or breathe in plague bacteria or get it from the bite of an infected flea. This is called exposure to plague. Not everybody who is exposed to plague will get sick. But many will, and as the plague bacteria multiply inside the body, they can cause serious illness.


Someone can get exposed to naturally-occurring plague by:

  • Getting bitten by a plague-infected flea.
  • Touching the fluid draining from the swollen gland of an untreated, plague-infected person.
  • Breathing in small drops that come from the coughs, sneezes or spit of people or animals with the lung form of plague (pneumonia).
  • Touching the body of an animal that died from plague.

Terrorists could use plague bacteria to hurt people on purpose by releasing the bacteria in public places.


What if there is a Plague Emergency in San Francisco?

The San Francisco Department of Public Health (SFDPH) has a plan to respond quickly to a plague emergency. SFDPH will evaluate the plague situation and may recommend ways for people to keep themselves and their family safe. Recommendations may include antibiotics for people who are at risk of illness. SFDPH will also participate in efforts to provide needed medical support and treatment, and to reduce any ongoing sources of plague bacteria.


How can I keep from Getting Plague?

To lower your risk of getting plague from a natural source:

  • Do not handle sick or dead animal bodies. But if you must, then use gloves plus face and eye protection.
  • Avoid rodents (mice, rats) and rodent droppings.
  • Avoid insect bites by using an insect repellent containing DEET.
  • Eliminate fleas from your home.
  • Avoid touching infected tissues, materials, or body fluids from a plague-infected person or animal.
  • Keep a minimum of 3 feet between you and anyone who may have the lung form of plague (pneumonia).
  • It is always a good idea to wash your hands regularly and avoid touching your eyes, nose, and mouth.

If terrorists release plague bacteria on purpose, check for recommendations from SFDPH.


Is there a Medicine to Prevent Plague disease?

Yes. If you have been exposed to plague, there are certain antibiotics you can take before you get sick as a way to prevent illness. These antibiotics can prevent plague disease even after the plague bacteria have already gotten into your body. They work best when you start taking them as soon as possible after plague exposure. In an emergency involving plague, SFDPH will announce which antibiotics to take, who should take them, how and where you can get them, and how to take them after exposure to plague.


Is there a Vaccine (shot) to Prevent Plague?

No, there is no vaccine for plague available now in the United States.


Can I catch Plague from Someone?

Yes. Plague is contagious (spread from person-to-person). You should keep a minimum of 3 feet between you and anyone who may have the lung form of plague, or who is coughing, sneezing, has a fever, or is short of breath. You should avoid touching infected tissues or body fluids from a plague-infected person or animal. You should also wash your hands often and avoid touching your eyes, nose, and mouth.


What are the Signs of Plague disease?

  • Lung (pneumonic) Plague is the most likely form of disease after an intentional release of plague and occurs by breathing in the plague bacteria. After exposure, it usually takes 1-4 days (sometimes up to 6 days) until illness starts. It may start with symptoms that seem like the common flu - fever, headache, cough, vomiting, and muscle aches - but will then progress quickly to pneumonia, with severe coughing, shortness of breath, and chest pain.
  • Bubonic Plague is the most common naturally-occurring form of plague and is caused by the bite of an infected flea. A sore usually forms at the site of the bite. Plague bacteria enter the skin and travel to the nearest lymph node (gland), usually in the groin, underarm, or neck. The lymph node becomes red, swollen, and painful, and can leak infected fluid. This swollen, draining lymph node is called a "bubo."
  • Septicemic (blood) Plague is a blood infection with plague bacteria. It can result from fleabites, touching plague-infected materials with broken skin, or spread of infection from the lung or bubo. Once plague bacteria are in the bloodstream, severe illness and death can follow quickly. Very rarely, humans develop plague meningitis (brain infection) or pharyngitis (throat infection).

See a doctor right away if you are having the signs listed above and you think you may have been exposed to plague. It is important to start medical treatment as soon as possible.


Is there Treatment for Plague disease?

Yes. All forms of plague can be treated with the proper antibiotics. Plague can be deadly however if no antibiotics are taken or if the antibiotics are taken too late.


How can I find Information during a Plague Emergency?

Check the SFDPH website Local media such as newspapers, TV stations and radio will carry emergency instructions. Emergency radio stations include: KCBS 740 AM and KGO 810 AM.


What can I do now if I am worried about plague?

  • Read about plague at and at the CDC page
  • Go to to learn about steps you can take now to prepare for all disasters.
  • Keep a card in your wallet with a list of your health problems, the names and doses of medicines you take, and any medicines you are allergic to.

Additional Information

  • Information on Plague for Health Care Providers
    • Reporting: A suspected or confirmed case of Plague must be reported immediately (within one hour) to SFDPH by calling (415) 554-2830. Click here for reporting information.
    • Documents:
      • "Infectious Disease Emergencies: A Preparedness and Response Guide for San Francisco Clinicians"

Other Links

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