- Scientific name: Yersinia pestis; a bacterium (not a virus)
- Plague is the disease that develops after infection with this bacterium.
- Humans contract plague by inhaling it or from the bite of an infected flea.
- Plague infection takes three primary forms:
- Only pneumonic plague is contagious through respiratory droplets with direct close contact (within 6 feet).
- Plague is highly lethal if untreated.
- Plague can be treated with antibiotics if caught early.
- Some plague infections occur naturally each year (usually bubonic).
Plague as a Weapon
Because pneumonic plague is highly lethal and contagious and would quickly overwhelm communities and their healthcare systems, countries with biological weapons programs have explored using plague in aerosol form to infect large groups of people.
- A pneumonic plague outbreak would be difficult to contain.
- Treatment must be immediate (within 24 hours of first symptoms) to be successful.
- Once refined, plague bacteria can be released into the air undetected.
- Once released into the air, plague bacteria remain infectious for up to an hour.
- Aerosolized plague bacteria can infect large groups of people quickly.
- Plague bacteria degrade quickly in sunlight or heat.
What We Don't Know About Plague as a Weapon
Experts are uncertain as to how wide an area would be affected by an aerosol release of plague bacteria or whether it can be disseminated successfully through the mail, as was the case with anthrax.
Identifying an Attack
A plague attack will most likely go unnoticed until people exhibit symptoms.
Tests of powder or residue can identify the presence of plague bacteria.
There are three common forms of illness caused by the plague bacteria:
- Bubonic plague is caused when infected fleas bite humans.
- A person can also be infected through a break in the skin.
- This form of plague illness is not contagious.
- Bubonic plague infects the lymphatic system and causes severe swelling.
- The first symptoms appear two to six days after infection and include weakness, high fever, and chills.
- If bubonic plague is not treated, bacteria can spread through the bloodstream, causing septicemic plague or a secondary case of pneumonic plague.
- Later symptoms appear, such as muscular pain, swelling of lymph glands, and seizures.
If untreated, bubonic plague is fatal in more than 50 percent of cases because of progression of the bacteria into the bloodstream.
- This form of the disease infects the lungs.
- It is caused by breathing in aerosolized plague.
- This illness can be transmitted from person to person through respiratory droplets with direct close contact (within 6 feet).
- Symptoms usually surface two to four days (range of one to six days) after exposure.
- Initial symptoms include high fever, cough, and chills, similar to the flu.
- Later symptoms include pneumonia and bloody sputum (coughing up blood).
Without early detection and treatment, the mortality rate from pneumonic plague is nearly 100 percent.
If treated, the mortality rate from pneumonic plague is still 50 percent.