Biological Health Threats

Anthrax | Botulism | Pneumonic Plague | Smallpox

September 11, 2001 resulted in renewed interest in many biological health threats. (Read about "Microorganisms") When a little later that year anthrax laced letters were sent to members of the news media and to members of Congress, suddenly a little known disease was in the headlines. Since that time the federal government has stockpiled millions of doses of smallpox vaccine and has started anew a vaccination program for a disease most thought had been eradicated.

Although interest in these diseases may be new, the diseases themselves are not.

Below, you'll find information on anthrax, botulism, plague and smallpox.

Anthrax

Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis. Anthrax most commonly occurs in hoofed mammals and can also infect humans. (Read about "Animal & Insect Borne Diseases")

The serious forms of human anthrax are:

• inhalation anthrax
• cutaneous anthrax
• intestinal anthrax

Symptoms of disease vary depending on how the disease was contracted, but usually occur within 7 days after exposure.

Initial symptoms of inhalation anthrax infection may resemble the flu. (Read about "Influenza") After several days, the symptoms may progress to severe breathing problems and shock. Inhalation anthrax is often fatal. (Read about "Occupational Respiratory Diseases")

According to the Centers for Disease Control and Prevention (CDC), most (about 95 percent) anthrax infections are cutaneous. They occur when the bacterium enters a cut or abrasion on the skin (Read about "Skin"), such as when handling contaminated wool, hides, leather or hair products (especially goat hair) of infected animals. Skin infection begins as a raised itchy bump that resembles an insect bite (Read about "Insect Bites") but within 1-2 days develops into a vesicle and then a painless ulcer, usually 1-3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the adjacent area may swell. About 20 percent of untreated cases of cutaneous anthrax will result in death. Deaths are rare with appropriate antimicrobial therapy.

The intestinal disease form of anthrax may follow the consumption of contaminated food and is characterized by an acute inflammation of the intestinal tract. (Read about "Digestive System") Initial signs of nausea, loss of appetite, vomiting, and fever are followed by abdominal pain, vomiting of blood and severe diarrhea. (Read about "Diarrhea") Intestinal anthrax results in death in 25 to 60 percent of cases.

In persons exposed to anthrax, infection can be prevented with antibiotic treatment. (Read about "Antibiotics") Early antibiotic treatment of anthrax is essential - delay lessens chances for survival. Anthrax usually is susceptible to penicillin, doxycycline and fluoroquinolones. An anthrax vaccine also can prevent infection. The Food and Drug Administration (FDA) is stressing that any antibiotic should only be used by those who really need it because unnecessary antibiotic use exposes patients to the risks of a drug without any potential benefit.

CDC says anthrax is not contagious and cannot be transmitted from person to person. The spread of anthrax through a deliberate bioterrorist act, however, is an ongoing concern.

Botulism

Botulism is a muscle-paralyzing disease caused by a toxin made by a bacterium called Clostridium botulinum. There are three main kinds of botulism:

• Foodborne botulism occurs when a person ingests pre-formed toxin that leads to illness within a few hours to days. Foodborne botulism is a public health emergency because the contaminated food may still be available to other persons besides the patient. (Read about "Food Safety")
• Infant botulism occurs in a small number of susceptible infants each year who harbor C. botulinum in their intestinal tract. (Read about "Digestive System")
• Wound botulism occurs when wounds are infected with C. botulinum that secretes the toxin. (Read about "Wound Care")

With foodborne botulism, symptoms begin within 6 hours to 2 weeks (most commonly between 12 and 36 hours) after eating toxin-containing food.

Symptoms of botulism include double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, muscle weakness that always descends through the body: first shoulders are affected, then upper arms, lower arms, thighs, calves, etc. Paralysis of breathing muscles can cause a person to stop breathing and die, unless assistance with breathing (mechanical ventilation) is provided.

Botulism is not spread from one person to another. Foodborne botulism can occur in all age groups. Antitoxin against botulism is effective in reducing the severity of symptoms if administered early in the course of the disease. Most patients eventually recover after weeks to months of supportive care.

A supply of antitoxin against botulism is maintained by CDC.

Pneumonic Plague

Plague is an infectious disease of animals and humans caused by the bacterium Yersinia pestis. Y. pestis is found in rodents and their fleas in many areas around the world. (Read about "Animal & Insect Borne Diseases") Pneumonic plague occurs when Y. pestis infects the lungs.

The first signs of illness in pneumonic plague are:

• fever
• headache
• weakness
• cough productive of bloody or watery sputum

The pneumonia (Read about "Pneumonia") progresses over 2 to 4 days and may cause septic shock and, without early treatment, death. (Read about septic shock in "Sepsis")

Person-to-person transmission of pneumonic plague occurs through respiratory droplets, which can only infect those who have face-to-face contact with the ill patient. (Read about "Respiratory System")

Early treatment of pneumonic plague is essential. Several antibiotics are effective, including streptomycin, tetracycline and chloramphenicol. (Read about "Antibiotics") There is no vaccine against plague. Prophylactic antibiotic treatment for 7 days will protect persons who have had face-to-face contact with infected patients.

Smallpox

Smallpox infection was eliminated from the world in 1977. It is, however, back in the news as a potential terrorist threat. Smallpox is caused by variola virus. The incubation period is about 12 days (range: 7 to 17 days) following exposure.

Initial symptoms include:

• high fever
• fatigue
• head and back aches

A characteristic rash, most prominent on the face, arms and legs, follows in 2-3 days. The rash starts with flat red lesions that evolve at the same rate. Lesions become pus-filled and begin to crust early in the second week. Scabs develop, then separate and fall off after about 3-4 weeks.

The majority of patients with smallpox should recover, but death occurs in up to 30 percent of cases. Smallpox is spread from one person to another by infected saliva droplets that expose a susceptible person having face-to-face contact with the ill person. Persons with smallpox are most infectious during the first week of illness, because that is when the largest amount of virus is present in saliva. However, some risk of transmission lasts until all scabs have fallen off.

Routine vaccination against smallpox ended in 1972. The level of immunity, if any, among persons who were vaccinated before 1972 is uncertain; therefore, these persons are assumed to be susceptible. In people exposed to smallpox, the vaccine can lessen the severity of or even prevent illness if given within 4 days after exposure. Vaccine against smallpox contains another live virus called vaccinia. The vaccine does not contain smallpox virus.

The United States has stockpiled enough smallpox vaccine to inoculate everyone in the country. A plan has been developed by the federal government to inoculate members of the military, healthcare workers and then the general public if they desire. A number of medical groups, including the American Medical Association, are urging a go slow process when it comes to inoculations. The issues raised by the groups concern side effects from the vaccine that can include about one to two deaths for every million people inoculated. Without a clear indication that smallpox is once again on the loose the medical groups question the value of mass inoculations. The CDC also warns eczema (Read about "Eczema") sufferers to avoid the vaccine, unless they know they have been exposed to smallpox, and to avoid people who have been recently inoculated for smallpox. The National Eczema Association for Science and Education says eczema sufferers have a heightened risk of life threatening reactions.

There is no proven treatment for smallpox but research to evaluate new antiviral agents is ongoing. If someone contracts smallpox they can benefit from supportive therapy (intravenous fluids, medicine to control fever or pain, etc.) and antibiotics for any secondary bacterial infections that occur. (Read about "Antibiotics")

The above information has been provided by the Centers for Disease Control and Prevention.

Related Information:

    The Immune System

    Immune System Glossary