Anthrax is a rare but serious illness caused by a spore-forming bacterium, Bacillus anthracis. Anthrax mainly affects livestock and wild game. Humans can become infected through direct or indirect contact with sick animals.
There's no evidence that anthrax is transmitted from person to person, but it's possible that anthrax skin lesions may be contagious through direct contact. Usually, anthrax bacteria enter the body through a wound in the skin. You can also become infected by eating contaminated meat or inhaling the spores.
Signs and symptoms, which depend on how you're infected, can range from skin sores to vomiting to shock. Prompt treatment with antibiotics can cure most anthrax infections. Inhaled anthrax is more difficult to treat and can be fatal.
You can contract anthrax when spores enter an open wound in your skin. The infection begins as a raised, sometimes itchy, bump resembling an insect bite. But within a day or two, the bump develops into an open, usually painless sore with a black center.
This illustration shows how the spores that cause inhalation anthrax — the most deadly form of anthrax infection — enter and affect the body.
There are four common routes of anthrax infection, each with different signs and symptoms. In most cases, symptoms develop within seven days of exposure to the bacteria. The one exception is inhalation anthrax. After exposure to inhalation anthrax, it may take weeks before symptoms appear.
A cutaneous anthrax infection enters your body through a cut or other sore on your skin. It's by far the most common route the disease takes. It's also the mildest — with appropriate treatment, cutaneous anthrax is seldom fatal. Signs and symptoms of cutaneous anthrax include:
- A raised, itchy bump resembling an insect bite that quickly develops into a painless sore with a black center
- Swelling in the sore and nearby lymph glands
This form of anthrax infection begins by eating undercooked meat from an infected animal. Signs and symptoms include:
- Abdominal pain
- Loss of appetite
- Severe, bloody diarrhea in the later stages of the disease
- Sore throat and difficulty swallowing
- Swollen neck
Inhalation (pulmonary) anthrax
Inhalation anthrax develops when you breathe in anthrax spores. It's the most deadly way to contract the disease, and even with treatment, it is often fatal. Initial signs and symptoms of inhalation anthrax include:
- Flu-like symptoms, such as sore throat, mild fever, fatigue and muscle aches, which may last a few hours or days
- Mild chest discomfort
- Shortness of breath
- Coughing up blood
- Painful swallowing
As the disease progresses, you may experience:
- High fever
- Trouble breathing
- Meningitis — a potentially life-threatening inflammation of the brain and spinal cord
This is the most recently identified route of anthrax infection. It's contracted through injecting illegal drugs and has been reported only in Europe so far. Initial signs and symptoms of injection anthrax include:
- Redness at the area of injection (without an area that changes to black)
- Significant swelling
As the disease progresses, you may experience:
- Multiple organ failure
When to see a doctor
Many common illnesses start with symptoms that resemble the flu. The chances that your sore throat and aching muscles are due to anthrax are extremely small.
If you think you may have been exposed — for example, if you work in an environment where anthrax is likely to occur — see a doctor immediately for evaluation and care. If you develop signs and symptoms of the disorder after exposure to animals or animal products in parts of the world where anthrax is common, seek prompt medical attention. Early diagnosis and treatment are crucial.
Anthrax spores are formed by anthrax bacteria that occur naturally in soil in most parts of the world. The spores can remain dormant for years until they find their way into a host. Common hosts for anthrax include wild or domestic livestock, such as sheep, cattle, horses and goats.
Although rare in the United States, anthrax is still common throughout the developing world, such as in Iran, Iraq, Turkey, Pakistan and sub-Saharan Africa.
Most human cases of anthrax occur as a result of exposure to infected animals or their meat or hides. In the United States, a few people have developed anthrax while making traditional African drums from the skins of infected animals.
One of the few known instances of nonanimal transmission occurred in the United States in 2001 when 22 people developed anthrax after being exposed to spores sent through the mail. Five of those who were infected died.
More recently, heroin users in Europe contracted anthrax through injecting illegal drugs. Eighteen people died from injectable anthrax. Heroin sold in Europe likely comes from areas where naturally occurring anthrax is more common.
To contract anthrax, you must come in direct contact with anthrax spores. This is more likely if you:
- Are in the military and deployed to an area with a high risk of exposure to anthrax
- Work with anthrax in a laboratory setting
- Handle animal skins, furs or wool from areas with a high incidence of anthrax
- Work in veterinary medicine, especially if you deal with livestock
- Handle or dress game animals — in the United States, seasonal outbreaks of anthrax are common among livestock and game animals, such as deer
- Inject illegal drugs, such as heroin
The most serious complication of anthrax is inflammation of the membranes and fluid covering the brain and spinal cord, leading to massive bleeding (hemorrhagic meningitis) and death.
Antibiotics are recommended to prevent infection in anyone exposed to the spores. Ciprofloxacin (Cipro), doxycycline (Monodox, Vibramycin, others) and levofloxacin (Levaquin) are approved by the Food and Drug Administration for post-exposure prevention of anthrax in adults and children.
An anthrax vaccine for humans is available. The vaccine doesn't contain live bacteria and can't lead to infection, but it can cause side effects, ranging from soreness at the injection site to more-serious allergic reactions.
The vaccine isn't intended for the general public. Instead, it's reserved for military personnel, scientists working with anthrax and people in other high-risk professions.
Avoiding infected animals
If you live or travel in a country where anthrax is common and herd animals aren't routinely vaccinated, avoid contact with livestock and animal skins as much as possible. Also avoid eating meat that hasn't been properly cooked.
Even in developed countries, it's important to handle any dead animal with care and to take precautions when working with or processing imported hides, fur or wool.