What Is It?

Caused by infection with the rod-shaped bacterium yersinia pestis, plague is one of the most deadly and potentially effective bioweapons. About 14 percent, or 1 in 7, of all plague cases in the United States are fatal. There are three forms - pneumonic plague, bubonic and septicemic plague. Pneumonic - the most harmful of the three and the one most likely to be used in an attack - has a lethality rate of almost 100 percent if untreated and 50 percent if treated. This form infects more easily than the other forms and is the only contagious form.

Millions of people in Europe died from plague in the Middle Ages, when human homes and places of work were inhabited by flea-infested rats. Human outbreaks occur in areas where housing and sanitation conditions are poor, in rural communities or in cities. During World War II, the Japanese army spread bubonic plague by dropping infected fleas over China.

The last U.S. urban plague epidemic occurred in Los Angeles in 1924-25. Since then, human plague in the United States has occurred as mostly scattered cases in rural areas - an average of 10 to 20 persons each year. The World Health Organization reports 1,000 to 3,000 cases of plague every year. In North America, plague is found in certain animals and their fleas from the Pacific Coast to the Great Plains, and from southwestern Canada to Mexico. Most human cases in the U.S. occur in two regions: 1) northern New Mexico, northern Arizona and southern Colorado; and 2) California, southern Oregon and far western Nevada. Plague also exists in Africa, Asia and South America.

While most outbreaks are of the bubonic type, outbreaks of pneumonic plague can become epidemics and cause public panic and chaos.

While plague is highly contagious and causes high fatality rates, its threat as a bioweapon may be lessened given its instability in the environment and the degree of technical sophistication it takes to refine it and spread it quickly and effectively.

How Is It Spread?

Bubonic plague - spread when people are bit by a rodent flea that is carrying the plague bacterium or by handling an infected animal. Contraction can also occur as a result of direct contact with infected tissues or fluids from handling sick or dead animals and with respiratory droplets from cats and humans with pneumonic plague. Bubonic plague is not contagious.

Pneumonic plague - results from the inhalation of the bacteria into the lungs or from the spread of infection of the septicemic form. Transmission can happen when a person with plague pneumonia coughs droplets containing the plague bacteria into air that is breathed by a non-infected person. Therefore, pneumonic plague is highly contagious.

Septicemic plague - occurs when the plague infection enters the bloodstream, leading to internal hemorrhaging and, without fast treatment, rapid death. This form is not contagious.

In the case of a bioterror attack, plague bacterium may also be released in an aerosolized form into the air. Another option for would-be evildoers is to release plague-infested rats or fleas into crowded areas.

What Are the Symptoms of Exposure?

Bubonic plague infects the lymphatic system. It causes enlarged, tender lymph nodes, fever, chills and extreme exhaustion. The swollen gland is called a "bubo" (hence the term "bubonic plague"). This type of plague should be suspected especially if a potential victim has a history of possible exposure to infected rodents, rabbits or fleas. A person usually becomes ill with bubonic plague two to six days after being infected and may even expel bloody sputum. If plague patients are not given specific antibiotic therapy, the disease can progress rapidly to death.

When bubonic plague is left untreated, plague bacteria invade the bloodstream. As the plague bacteria multiply in the bloodstream, they spread rapidly throughout the body and cause a severe and often fatal condition.

Septicemic plague causes fever, chills, prostration, abdominal pain, shock and bleeding into skin and other organs.

Pneumonic plague causes fever, chills, cough-producing bloody mucus, difficulty breathing, diarrhea, nausea and vomiting. Rapid shock and death will take place if not treated early. Symptoms appear two to four days after it's inhaled into the lungs. A full pulmonary infection follows the first symptoms, and death can follow within a day or two if the victim is not treated early.

How Is It Treated?

Today, modern antibiotics are effective against plague, but if an infected person is not treated promptly, the disease is likely to cause illness or death. No viable plague vaccine exists.

Pneumonic plague requires antibiotics within 24 hours of exposure.

According to treatment experts, a patient diagnosed with suspected plague should be hospitalized and medically isolated. Antibiotic treatment should begin as soon as possible after laboratory specimens are taken. Streptomycin is the antibiotic of choice. Gentamicin is used when streptomycin is not available. Tetracyclines and chloramphenicol are also effective.

Persons who have been in close contact with a plague patient, particularly a patient with plague pneumonia, should be identified and evaluated. The U.S. Public Health Service requires that all cases of suspected plague be reported immediately to local and state health departments and that the diagnosis be confirmed by the CDC. As required by the International Health Regulations, the CDC reports all U.S. plague cases to the World Health Organization.

Who Has It/Where Can It Be Found?

Labs around the world study plague bacteria. Although the samples are usually protected, there are no real guarantees that the safeguards are 100 percent foolproof. Plague was one biowarfare agent intensely studied and produced by the hundreds of tons by the Soviet Union before Biopreparat was terminated. Not only is the fate of that stockpile unknown, but so is the present locations of many of the scientists who helped make the plague a weapon.

More recently, Iraq and North Korea are thought to have conducted bioweapons research with plague bacteria.