First signs
All forms begin abruptly, usually within one to seven days of infection, with fever, chills, headache, body aches and marked weakness, often with nausea and vomiting. ECDC describes it as flu-like symptoms that "rapidly progress" into serious illness. These early signs are not specific: what points to plague is a recent possible exposure.
Symptoms by form
Pneumonic plague
Infection of the lungs. The only form that spreads from person to person, through respiratory droplets.
- Sudden high fever, headache, weakness
- Rapid pneumonia: shortness of breath, chest pain
- Cough, sometimes with bloody or watery sputum
Incubation: As short as 24 hours (WHO); usually 1 to 3 days (CDC). Untreated: Always fatal; can kill within 18 to 24 hours.
Bubonic plague
The most common form, usually from a flea bite. Bacteria multiply in the nearest lymph node, which swells into a painful bubo.
- Sudden fever, chills, headache, weakness
- One or more swollen, tender lymph nodes (groin, armpit, neck)
Incubation: 1 to 7 days (WHO); 2 to 8 days (CDC). Untreated: 30 to 60 percent fatal.
Septicemic plague
Bacteria multiply in the bloodstream, either as the first sign or after untreated bubonic plague.
- Fever, chills, extreme weakness, abdominal pain, shock
- Bleeding under the skin; blackened fingers, toes or nose
Incubation: Days; often follows the bubonic form. Untreated: Always fatal without treatment (WHO).
Septicemic plague
In septicemic plague the bacteria multiply in the bloodstream, either as the first sign of infection or after untreated bubonic plague. Patients have fever, chills, extreme weakness, abdominal pain, nausea, vomiting or diarrhoea, and can go into shock. Bleeding under the skin, a bluish discolouration and tissue death in the fingers, toes or nose, which can turn black, are typical. WHO describes it as always fatal without treatment.
Rarer forms include plague meningitis, usually a complication of late or inadequate treatment, and pharyngeal plague, a throat infection after eating undercooked infected meat.
Incubation periods
- Pneumonic: as short as 24 hours (WHO); 1 to 3 days (CDC, ECDC).
- Bubonic: 1 to 7 days (WHO); 2 to 8 days (CDC); 2 to 6 days (ECDC).
- Septicemic: poorly defined, likely within days (CDC); 2 to 6 days when primary (ECDC).
When to seek emergency care
Call an emergency number at once, and say why, if you develop sudden fever plus any of the following after a possible exposure (contact with a plague patient, a sick or dead animal in an endemic area, flea bites there, or a laboratory incident):
- a painful, swollen lymph node
- cough, chest pain or shortness of breath, especially with bloody sputum
- signs of shock: confusion, cold clammy skin, very fast pulse
Doctors are instructed to start antibiotics as soon as plague is suspected, without waiting for test results.
How it is diagnosed
Confirmation requires the laboratory: Y. pestis is identified in pus from a bubo, blood or sputum by culture or PCR. A rapid dipstick test for the F1 antigen is widely used in Africa and South America, but WHO says positives must be confirmed by culture or PCR. Under the microscope the bacteria show a characteristic "safety pin" staining, the shape in our logo.
Reference information, not medical advice. With symptoms after a possible exposure, call your local emergency number.