Anthrax

Anthrax (AN-thraks) is a rare infectious disease caused by the bacterium Bacillus anthracis.

What Is Anthrax?

Anthrax is primarily a disease of livestock, such as sheep, cattle, or goats. It is rarely seen in humans, and most cases occur in developing countries. Anthrax is most likely to occur in people whose work regularly

brings them into contact with animal hides, such as those who cut sheep's wool, livestock handlers, laboratory workers, and veterinarians. The bacterium Bacillus anthracis (buh-SIH-lus an-THRA Y-kus) is found naturally in the soil of farming regions all over the world, including parts of the United States. It can exist undisturbed for many years as spores, a temporarily inactive form of the organism with a protective, shell-like coating. Grazing animals typically become infected with anthrax if they eat vegetation or feed contaminated with spores. Livestock in the United States rarely get anthrax.

There are three forms of anthrax in humans, each resulting from a different route of infection. Cutaneous (kyoo-TAY-nee-us), or skin, anthrax, the least serious form of the disease, occurs when the bacteria enter a break in the skin. Gastrointestinal ^* anthrax is caused by eating food contaminated with anthrax bacteria; this form is very rare. The third and deadliest form of the disease, inhalation (in-huh-LAY-shun) anthrax, also called pulmonary anthrax or "woolsorter's disease," is also very uncommon and results from breathing in anthrax spores.

How Common Is Anthrax?

Historians believe that anthrax has been around for thousands of years, at least since the fifth and sixth plagues described in the Bible's Book of Exodus. Cutaneous anthrax, the most common form of the disease (about 95 percent of anthrax cases), occurs most often in agricultural regions in Asia, Africa, South and Central America, southern and eastern Europe, the Middle East, and the Caribbean. Anthrax is rare in the United States: according to the U.S. Centers for Disease Control and Prevention, between 1955 and 1999 only 236 cases of anthrax were reported in the United States, nearly all the cutaneous form. Before 2001 the last case of inhalation anthrax in the United States was reported in 1978.

How Does a Person Get Anthrax?

Scientists do not believe that anthrax can be passed from person to person. Cutaneous anthrax occurs when someone with a cut, sore, or other break in the skin touches an infected animal or the by-product of an infected animal, such as contaminated hide, wool, or goat hair. Gastrointestinal anthrax usually is traced to contaminated foods, especially undercooked meat. Inhalation anthrax stems from breathing anthrax spores into the lungs. Although spores are inactive forms of the bacteria, they germinate, or become activated, in the moist, warm environment of the lungs. Someone has to inhale thousands of spores to contract the disease, and spores found in soil rarely are concentrated enough to cause inhalation anthrax.

What Are the Signs and Symptoms?

Symptoms of the disease usually appear within 1 to 7 days after infection with Bacillus anthracis and differ according to the way in which a person became infected with the bacterium. The most visible sign of cutaneous anthrax explains how the disease got its name, which is derived from the Greek word anthracis, meaning "coal." An anthrax skin infection typically begins as a raised, itchy bump, and within a few days it develops into a small sore or ulcer ^* with a black, coal-like center. Gastrointestinal anthrax can cause nausea, loss of appetite, fever, and severe bloody vomiting and diarrhea. The first symptoms of inhalation anthrax often resemble those of a common cold or influenza and include cough, difficulty in swallowing, headache, swollen lymph nodes ^* in the neck, and tiredness. Within days the symptoms rapidly progress to severe breathing problems and shock ^* , often leading to heart failure and death.

How Do Doctors Make the Diagnosis?

Bacillus anthracis bacteria sometimes can be seen in a bit of skin from the sore of a person who has cutaneous anthrax or in the coughed-up mucus ^* of someone with inhalation anthrax when those samples are viewed under a microscope. To help confirm the diagnosis, samples of blood or fluid taken from the nose or sores are cultured ^* to identify the anthrax bacteria. Blood tests also are used to detect anthrax antibodies ^* , which indicate that someone has come into contact with anthrax-causing bacteria and may have the disease. Chest X rays can help diagnose inhalation anthrax.

What Is the Treatment for Anthrax?

Doctors prescribe antibiotics to fight anthrax infections. Patients with gastrointestinal and inhalation anthrax typically need intensive, round-the-clock care with intravenous ^* medications and fluids in a hospital. Inhalation anthrax can cause severe breathing problems that may require the use of a respirator, a machine that can assist a person's breathing until he or she recovers.

What to Expect

Untreated, all three forms of anthrax can lead to widespread infection and death. If it is treated, cutaneous anthrax generally is not fatal. Gastrointestinal anthrax results in death in about half of all cases. Even with medical treatment, inhalation anthrax is often fatal.

How Is Anthrax Prevented?

Agricultural and textile workers in developed countries such as the United States are instructed to wash their hands after working in the soil or handling animals and animal by-products. People who live in high-risk areas of the world are advised to avoid contact with livestock and not to eat improperly prepared or undercooked meat. An anthrax vaccine ^* exists, but this vaccine is not given routinely in the United States, except to people in the military or to scientists who may come into contact with the bacteria through their research. Veterinarians and people whose jobs involve handling livestock typically are vaccinated against the disease if they work in high-risk areas of the world. In the fall of 2001, when anthrax spores contaminated several U.S. post offices and office buildings (see sidebar), public health experts recommended antibiotics for people who had been exposed to anthrax—even if they had no symptoms of the disease. Officials stressed, however, that it was not necessary or advisable for the general public to take antibiotics to prevent anthrax.