Anthrax

Anthrax is an infectious disease you get from a bacterium called Bacillus anthracis. This germ usually spreads to humans from animals, especially livestock. Human cases of anthrax are rare in developed nations. Only four confirmed cases happened in the U.S. from 2016 to 2024.

Anthrax turns itself into a spore form when it needs to survive harsher conditions. That form has a tough outer shell and can live for decades. When the spore infects you, it turns back to the bacterial form and makes toxins (poisons) that make you sick.

Types of anthrax

Anthrax in humans can take several forms. The one you have depends on where in your body the infection starts. The forms are:

• Cutaneous (skin)
• Gastrointestinal (digestive tract)
• Inhalational (lungs)
• Injection (under skin or in muscle)
• Welder’s anthrax (only seen in metalworkers)

Symptoms of anthrax

The symptoms of anthrax depend on which form you have.

Cutaneous anthrax symptoms

Skin anthrax starts as a small, red bump (papule). These form about five to seven days after the bacteria enter your skin. That’s more likely to happen through cuts or scrapes. The most likely place for this is on your hands, arms, neck or face.

The bump will grow into a blister-like lesion. It often doesn’t hurt early on, but it does itch. When it bursts, it causes an open wound. That wound will form a black, hard, scablike covering called eschar. More wounds like this can form around the first one.

The area around these wounds usually has some swelling. Inflamed, swollen lymph nodes (lymphadenopathy) or lymph vessels (lymphangitis) nearby can also happen.

Gastrointestinal anthrax symptoms

You can get anthrax in your throat (esophagus) or your stomach. If it’s in your throat, you might have:

• Trouble swallowing (dysphagia)
• Sore throat
• Throat or neck swelling
• Trouble breathing

The second form is in your stomach or lower digestive tract. Symptoms there include:

• Abdominal pain
• Abdominal fluid buildup and swelling (ascites)
• Diarrhea (often bloody)
• Malaise
• Nausea
• Red face and eyes
• Vomiting (often bloody)

Some people will have symptoms in stages. The symptoms will happen first in the throat and then later in the stomach and lower digestive tract.

Inhalational anthrax symptoms

Breathing in anthrax tends to cause symptoms in two phases. The first phase symptoms are often vague, like fatigue and a fever, and can look like the flu.

The second phase symptoms are usually more severe and can include:

• Chest pain
• Coughing, especially coughing blood (hemoptysis)
• Confusion
• Excessive sweating (diaphoresis)
• Fast, shallow breathing (tachypnea)
• Fast heartbeat (tachycardia)
• Headache (usually severe)
• Nausea
• Trouble breathing (dyspnea)

Injection anthrax symptoms

Injection anthrax is similar to cutaneous anthrax, but deeper. It can cause pockets of infection (abscesses) under your skin or in your muscles, but not many symptoms.

Those abscesses may cause an unusual amount of swelling, but little pain. The infection also doesn’t cause a fever or the scablike eschar seen with cutaneous anthrax.

Injection anthrax usually causes systemic effects. That means it has similar effects to diseases like sepsis and meningitis, and can quickly cause death.

Anthrax causes

While Bacillus anthracis causes anthrax disease in animals and humans, it’s not the bacteria themselves that make you sick. Instead, it’s two toxins (poisons) that the bacteria make. Those toxins are most dangerous to your heart and circulatory (cardiovascular) system and your liver. They can also severely disrupt your immune system. How you got the bacteria often depends partly on which form of anthrax you have:

• Cutaneous anthrax: This is the most common form and mainly happens when people get the bacteria through cuts or scrapes. People working with infected animals (alive or dead) or animal products like hides, hair or wool are most at risk.
• Gastrointestinal anthrax: This form happens when you eat undercooked meat from a sick animal.
• Inhalational anthrax: This form used to happen to people working with contaminated animal products. Nowadays, it’s rare. Bioterrorism is another possible source, but this is rare, too.
• Injection anthrax: This usually only happens with injection use of addictive substances. The first confirmed case happened in 2000. Confirmed outbreaks have happened in the United Kingdom and Europe, but not in the U.S.

How is anthrax transmitted?

There are two main ways that anthrax spreads:

• From animals to humans directly: That’s why experts classify it as a zoonotic disease.
• Spores that enter your body: When an infected animal or person dies from anthrax, bacteria from them can infect you directly or turn into spores. The spores can then later infect other people or animals.

Direct spread of anthrax from animals to people is rare in developed nations. That’s mainly due to widespread animal vaccination. Properly disposing of bodies (animal or human) also helps keep the spores from spreading.

There’s no evidence that anthrax can spread from person to person. If multiple people in one place get it, they usually get it from the same source.

Complications of anthrax

Anthrax complications often happen when the bacteria spread to other places in your body. That makes them very dangerous. Some of the more common complications include:

• Meningitis or meningoencephalitis (from any form of anthrax)
• Pleural effusion or similar effects (from inhalational anthrax)
• Pneumonia or mediastinitis (from inhalational anthrax)
• Sepsis (from any form of anthrax)
• Spreading infections or inflammation, like vasculitis or cellulitis (especially from cutaneous and injection anthrax)
• Stomach ulcers (from gastrointestinal anthrax)

How doctors diagnose anthrax

Healthcare providers diagnose anthrax using multiple methods. They’ll start with a physical exam, especially looking closely at any wounds you have and listening to your breathing. Depending on which type of anthrax you have, they may use different types of imaging and lab tests, too.

Some of the tests they may run include:

• Skin biopsy for cutaneous anthrax
• Blood tests like ELISA or PCR for all forms of anthrax
• Lumbar puncture (spinal tap) to check your cerebrospinal fluid (CSF) for all forms of anthrax
• Chest X-ray or CT scan for inhalational anthrax

A pathologist will often look at tissue or blood samples directly. Seeing Bacillus anthracis under a microscope can help with diagnosis.

How is anthrax treated?

Anthrax treatment can involve multiple approaches, depending on the form you have. Some of the most common treatments include:

• Antibiotics: Oral pills and intravenous (IV) antibiotics are key for treating anthrax. The main antibiotics providers will use are ciprofloxacin (Cipro®) or doxycycline (Monodox™ or Doryx®).
• Anthrax antitoxin (Anthrasil®): This is like an antidote that keeps anthrax toxins from attacking your cells.
• Monoclonal antibodies: Anthrax toxins use a special antibody to get into your cells. Monoclonal antibody medications like raxibacumab (Abthrax™) or oblitoxaximab (Anthim®) can block that antibody. That protects your cells from the toxin’s harmful effects.
• Anthrax vaccine (Biothrax® or Cyfendus®): Anthrax can sometimes take days or weeks to appear after it infects you. Providers will often give you the vaccine to prevent a delayed appearance.

You might need other treatments, depending on the form of anthrax you have and your health history. Your healthcare provider can tell you more about and recommend possible treatments.

Recovery time

The recovery time after treatment varies. For simpler cases of cutaneous anthrax, you may only need days or a few weeks. For more severe cases like inhalational anthrax, you might need long-term treatment over weeks or months. Your healthcare provider can tell you what to expect in your case.

What can I expect if I have this condition?

If you think you have anthrax or were exposed to it, get medical care as soon as you can. Call your healthcare provider or go to the nearest hospital or emergency room.

Your odds of survival depend strongly on the form of anthrax you have, how fast you got treatment and more. Some basic statistics about anthrax include:

Can anthrax be prevented?

Anthrax is preventable thanks to vaccines. For most people, that vaccine isn’t necessary because they won’t be exposed to anthrax in their everyday lives. But if you work in certain jobs, a vaccine might make a big difference. And some high-risk jobs require vaccination.

If you think or know you were exposed to anthrax, don’t panic. You can still get post-exposure prophylaxis (PEP) treatments. Those can keep you from developing this disease even after exposure. PEP for anthrax often involves getting an anthrax vaccination, antibiotics or both. Talk to your healthcare provider as soon as possible so you can start receiving PEP treatments.

What is welder’s anthrax?

Welder’s anthrax is a rare disease that looks a lot like inhalational anthrax. But Bacillus anthracis doesn’t cause it. Instead, rare strains of a related bacterium called Bacillus cereus are the cause. Like Bacillus anthracis, they also produce deadly toxins. Between 1997 and 2020, experts confirmed seven cases of this condition. They all happened in welders and metalworkers.

Researchers are still trying to figure out why this disease is so specific to welders and related professions. If you’re a welder or metalworker and have pneumonia symptoms, especially coughing up blood, you need to get medical care right away.

Is anthrax a biological weapon?

Yes, anthrax can be a biological weapon. Anthrax was used as a weapon in both world wars, and multiple countries have experimented with it. In 2001, a U.S. military researcher sent anthrax in letters via the U.S. Postal Service. A total of 22 people developed anthrax, and 5 of them died. The U.S. government now stockpiles anthrax antitoxin for emergency use in case of terrorist attacks.f