Plague

Jump to
Transmission
Symptoms and Treatment
Prevention
Plague Detections in San Diego County
Additional Information

About Plague

Plague is a potentially serious disease caused by the bacteria Yersinia pestis. It can be carried by rodents such as ground squirrels, chipmunks, wood rats, and mice.

Plague can be cured with antibiotics, but treatment must be given quickly. Humans usually become infected through the bite of an infected flea or by handling an infected animal.

The Vector Control Program routinely collects and tests fleas and blood samples from squirrels in our local mountains and campgrounds. If tests come back positive for plague, park rangers are notified and warning signs are posted to inform the public on how to avoid fleas and protect themselves and their pets. Rodent burrows may be treated with flea powder. The powder gets in the rodents' fur after they enter, killing fleas inside the burrow. This is very effective and does not harm rodents.

Transmission

Plague can be transmitted to people and animals by:

Bites from infected fleas - Hungry fleas will leave a sick or dead rodent to find new blood meals.

Direct contact with sick or dead animals - Plague bacteria in the blood, urine, or saliva of an infected animal can enter cuts and abrasions.

Pet involvement - Infected rodent fleas can be brought into a home or campsite by a dog or cat. Plague pneumonia can be transmitted by a sick cat that is coughing and sneezing.

Symptoms and Treatment

The early symptoms of plague usually appear two to eight days after exposure. These include nausea, vomiting, fever, chills, muscle aches, headache, and weakness.

Three forms of plague are known:

Bubonic plague

The most common form. It is characterized by swollen and tender lymph nodes (called "buboes") in the groin, neck, or armpit.

Septicemic plague

Plague bacteria infect the bloodstream, causing high fever, fatigue, weakness, and bleeding disorders.

Pneumonic plague

An infection of the lungs that can follow bubonic or septicemic plague. It can also occur directly from inhalation of plague bacteria. Patients with pneumonic plague have difficulty breathing, develop a cough, and may spit up blood-tinged saliva.

Plague is a very serious illness but treatable with antibiotics. The earlier a patient seeks medical care and receives treatment, the better their chances are of a full recovery.

If you have symptoms like those listed here, seek medical attention right away. Prompt treatment with the correct medications is critical to prevent complications or death.

Pets can also become sick from plague. An animal with plague will become very ill, may stop eating and will have a fever. Swollen lymph glands may occur, generally in the neck area.

Inform your veterinarian if a pet becomes sick following a visit to a plague area.

Prevention

When visiting, hiking, camping, or living in areas where plague occurs, avoid contact with wild rodents and their fleas.

Avoid known plague areas.
Avoid contact with wild animals and their fleas, especially sick or dead rodents.
Report sick or dead animals to park rangers or the Vector Control Program.
Use flea control products on pets.
Use caution when handling a sick pet that has been in a plague area.
Avoid face-to-face contact with sick pets or sick humans.
Contact a doctor right away if you become ill within 8 days of being in a plague area.

Plague Detections in San Diego County

Year	Total Positives	Community and Location(s)
2024	0	-
2023	0	-
2022	0	-
2021	0	-
2020	0	-
2019	0	-
2018	1	Tecate - Border Area
2017	2	Palomar - Doane Campground, Cedar Grove Campground
2016	0	-
2015	1*	Palomar - Cedar Grove Campground
2014	13*	Palomar - Doane Campground, Cedar Grove Campground, Fry Creek, Camp Palomar
2013	8	Palomar - Doane Campground, Cedar Grove Campground, Fry Creek
2012	4	Palomar - Doane Campground, Cedar Grove Campground
2011	0	-
2010	1	Palomar - Doane Campground
2009	3	Palomar - Doane Campground
2008	9	Palomar - Doane Campground, Cedar Grove Campground