What exactly is anthrax, and should you be worried about it?

Anthrax is an infection caused by a bacterium (a type of germ) called Bacillus anthracis (B. anthracis). Although it's most commonly seen in grazing animals like sheep, pigs, cattle, horses, and goats, anthrax also can occur in humans — although it's very rare.

In the environment, the anthrax-causing bacterium forms spores (a version of the germ covered by a hard protective shell) that can live in the soil for years. People can become infected by coming into contact with these spores through a break in the skin (such as a cut or scrape), by eating food (usually undercooked meat) contaminated by them, or by inhaling spores (breathing them into the lungs). But anthrax is not contagious, which means that it can't spread from person to person.

It's extremely unlikely that you or someone you know could get anthrax. In fact, there are usually only one or two reported cases of anthrax per year. Most of these have been in people who work with animals or animal products.

Why Are People So Concerned?

Anthrax that occurs naturally in the environment isn't a huge threat. But B. anthracis can be grown in a laboratory and some people are worried about anthrax germs being grown as a weapon.

The issue of laboratory-grown B. anthracis received lots of attention in 2001 after an anthrax outbreak in the United States. The outbreak scared many people, in part because five people died (which is very rare) and also because the outbreak coincided with the September 11 terrorist attacks. However, bioterrorism experts believe that it is technologically difficult to use anthrax effectively as a weapon on a large scale.

Types of Anthrax

The three main types of anthrax are:

1. Cutaneous or skin anthrax, can occur if someone with a cut or scrape handles contaminated animals or animal products. More than 95% of anthrax cases are of the cutaneous type, which is the least dangerous form. A person with cutaneous anthrax will notice a small sore that develops into a painless ulcer with a black area in its center. If left untreated, the infection can spread to other areas of the body.
2. Intestinal anthrax can occur if someone eats undercooked contaminated meat. Intestinal anthrax is far less common than cutaneous anthrax, but it can make someone much sicker. Intestinal anthrax symptoms include severe abdominal pain, nausea, vomiting, severe diarrhea, and bleeding from the digestive tract.
3. Pulmonary, or inhaled, anthrax is the rarest form of anthrax — but it's also the most dangerous. Pulmonary anthrax can only occur if someone breathes thousands of anthrax spores into the lungs. Pulmonary anthrax usually seems like a common cold or the flu at first, but it rapidly turns into severe pneumonia and requires hospitalization.

It usually takes fewer than 7 days for a person to show signs of anthrax after being infected. However, symptoms of pulmonary anthrax can sometimes take months to appear.

Is It Hard to Get Anthrax?

It's very difficult to get anthrax. Just being exposed to the spores or coming into contact with an infected animal doesn't mean that a person will automatically develop the disease.

For example, to get pulmonary anthrax (the type of anthrax that killed the five people in the 2001 outbreak), a person has to inhale thousands of spores. This is extremely difficult to do when the anthrax spores are found in soil or on infected animals.

Even in the case of the manmade outbreak in 2001, several of the people who were exposed were found to have B. anthracis spores only in their nostrils when tested. These spores hadn't made it to their lungs in sufficient amounts to cause a problem. In other words, the people had been exposed to the bacteria but had not developed the disease.

How Is Anthrax Diagnosed and Treated?

Medical professionals can diagnose anthrax by taking samples from the skin sores, blood, or other bodily fluids of people who are believed to have been exposed to B. anthracis. These samples are then sent to a lab to check whether the person has the bacteria in his or her system.

If anthrax is caught early, it is almost always successfully treated with antibiotics. If a person is known to have been exposed to B. anthracis but has no signs or symptoms of the disease, antibiotics may be given (after exposure) to prevent the disease from occurring.

Although there is a vaccine for anthrax, in the United States it is currently only recommended for people who are at risk of coming into contact with B. anthracis. They include people who work with B. anthracis in laboratories, people who handle potentially infected animal products, and U.S. military personnel. The vaccine is not given routinely to people in the United States and it hasn't been studied for use in people younger than 18.

If you worry when you hear about anthrax, remember that it's very rare, and it's unlikely that you will ever be exposed to the germs that cause anthrax. If you're worried about it, talk to a science teacher or medical professional — someone who can help you find the answers to any questions you may have about anthrax.

Reviewed by: Steven Dowshen, MD
Date reviewed: January 2013