OVERVIEW

What is anthrax?

Anthrax is a group of zoonotic diseases caused by Bacillus anthracis, primarily affecting herbivorous animals such as cattle and sheep. Humans can become infected through contact with animals suffering from anthrax or their products, or through exposure to Bacillus anthracis and its spores in the air or soil.

Anthrax mainly includes cutaneous anthrax, pulmonary anthrax, gastrointestinal anthrax, injectional anthrax, and some other rare types (such as anthrax meningitis).

The onset of anthrax is insidious, with a lack of specificity in the early stages. However, once typical symptoms appear, the disease can rapidly progress to severe stages such as sepsis and multiple organ failure within 2–3 days, with an extremely high mortality rate.

The first-line treatment for anthrax is penicillin. If diagnosed and treated early, some patients can be cured.

Why can Bacillus anthracis be used as a biological weapon or for bioterrorism?

• The spores of Bacillus anthracis are highly resistant to heat and common chemical disinfectants. They can survive in dry soil or animal hides for years to decades. Once a pasture is contaminated, the infectivity can persist for decades. If animal products are contaminated with spores, ordinary boiling or soaking in disinfectants cannot kill the spores—only high-pressure sterilization is effective.

• The onset of anthrax is insidious, with a lack of specificity in the early stages. However, once typical symptoms appear, the disease can rapidly progress to severe stages such as sepsis and multiple organ failure within 2–3 days, with an extremely high mortality rate.

Therefore, Bacillus anthracis is often used as a biological weapon, and countries maintain extremely strict surveillance of anthrax.

SYMPTOMS

What are the types of anthrax? What are the symptoms?

• Cutaneous anthrax: This type accounts for over 95% of all anthrax cases. It commonly occurs on exposed areas such as the arms, hands, face, and neck. Initially, it appears as a small local scab, followed by surrounding blisters and pustules resembling insect bites. Eventually, it forms necrotic ulcers with a characteristic black eschar, measuring 1–3 cm in diameter, hence the name "anthrax." About 20% of patients develop systemic infection symptoms such as high fever, muscle and joint pain, and bleeding, which can be fatal.
• Inhalation anthrax: This occurs when dust containing large amounts of Bacillus anthracis spores is inhaled. The incubation period is about 6 weeks. Patients develop respiratory symptoms such as coughing, sputum production, and chest pain (primarily in the lower chest). Symptoms gradually worsen, leading to systemic infection and toxicosis, including gastrointestinal ulcers and septicemia, ultimately resulting in death.
• Gastrointestinal anthrax: This is rare and usually caused by consuming undercooked infected meat, milk, or contaminated food. Patients initially experience digestive symptoms such as vomiting, diarrhea, and abdominal pain, followed by systemic infection and toxicosis.
• Injection anthrax: In recent years, another form of anthrax infection has been identified among injection drug users. Its symptoms resemble cutaneous anthrax, but the infection penetrates deeper into the skin or muscles at the injection site, spreads more rapidly throughout the body, and is harder to diagnose and treat.
• There are also rare subtypes, such as anthrax meningitis, which progresses rapidly with symptoms like severe headache, vomiting, confusion, and seizures. Most patients die within days of onset.

CAUSES

What are the routes of anthrax infection?

Anthrax can enter the human body through the digestive tract, respiratory tract, or skin contact, but human-to-human transmission is relatively rare.

• Pulmonary (Inhalation) Anthrax: In the early stages of respiratory infection, symptoms resemble those of a common cold or flu for several days, followed by severe, even fatal, respiratory failure. If not treated immediately after exposure before symptoms appear, the mortality rate exceeds 85%. The lethal dose of inhaled anthrax ranges between 10,000 to 20,000 spores of Bacillus anthracis. However, timely treatment can reduce the fatality rate to 45%. Due to historical factors and the distribution of Bacillus anthracis in nature, this form of anthrax was first observed among ranch workers exposed to large amounts of livestock waste or leather-related products, as well as those frequently in contact with soil, hence its alternative names "woolsorter's disease" or "ragpicker's disease." Other potential exposure factors include processing animal horns, hair, or hides.
• Gastrointestinal Anthrax: Infection of the gastrointestinal tract is accompanied by symptoms such as vomiting blood, severe diarrhea, acute enteritis, and loss of appetite.
• Cutaneous Anthrax: Skin anthrax infection manifests within 1–2 weeks, initially appearing as an irritating, itchy skin lesion or a black spot-like blister resembling black mold commonly found on stale bread. This later develops into a large, painless necrotic ulcer. Unlike ordinary bruises or most other skin lesions, cutaneous anthrax does not cause pain. Without treatment, it still carries a 20% mortality rate, which, while lower than other forms of anthrax, remains a very high figure in medical statistics. However, with treatment, the risk is almost negligible.

Can anthrax spread between humans?

Anthrax is generally considered non-contagious, meaning it is not easily transmitted through routine contact with an infected person, unlike the common cold or flu. However, isolated cases have been reported where individuals contracted the disease after contact with skin lesions of cutaneous anthrax patients, suggesting that cutaneous anthrax may have some degree of contagiousness, though this has not been confirmed.

DIAGNOSIS

How is anthrax diagnosed?

• Medical history and symptoms: Exposure to sick animals, suspicious dust, trauma history, characteristic skin lesions, chest pain, cough with sputum, nausea, vomiting, etc.
• Laboratory diagnosis: Microscopic examination of wound exudate or blood may reveal the bacteria. Culturing and identifying specimens on bacterial culture plates is the "gold standard" for diagnosis, though time-consuming and labor-intensive with a high false-negative rate. Currently, serological methods to detect anthrax antibodies in blood are more commonly used due to their speed and convenience, though they are prone to interference and have a certain false-positive rate.

TREATMENT

Which department should I visit for anthrax?

Infectious Disease Department. Depending on the type of infection, you may also need to visit relevant departments such as Dermatology, Respiratory Medicine, or Gastroenterology.

How is anthrax treated? Can it be cured?

Bacillus anthracis is sensitive to various antibiotics including penicillin, erythromycin, and chloramphenicol, with penicillin being the first-line treatment. If detected and treated promptly, some patients can be cured.

DIET & LIFESTYLE

Do anthrax patients need to be isolated?

Yes. Once anthrax patients are identified, they must be isolated immediately. Cutaneous anthrax is managed as a Category B notifiable infectious disease, while pulmonary anthrax is managed as a Category A notifiable infectious disease.

The patient's secretions and excretions must be thoroughly disinfected, and isolation can only be lifted after complete recovery.

What should I do if I have been in contact with an anthrax patient?

Medical observation for 8 days is required.

PREVENTION

How to Prevent Anthrax?

• Prevention of anthrax should focus on controlling livestock infections and pasture contamination. Infected animals must be strictly isolated or euthanized and buried deeply. Dead animals must not be skinned, dissected, or cooked—they must be incinerated or buried at least 2 meters underground. Contaminated animal products should undergo high-temperature and high-pressure sterilization. Properly handle contaminated protective materials such as clothing and gloves (disinfect or incinerate).
• For people in epidemic areas, immunization with attenuated live anthrax vaccines is recommended, providing immunity for up to one year.
• There have been multiple cases of anthrax spores being spread through mail in Europe and the U.S. Therefore, avoiding opening suspicious mail is crucial for preventing bioterrorism attacks.

Is the Attenuated Live Anthrax Vaccine Safe?

An attenuated live vaccine is produced by cultivating, modifying, and screening strains under controlled conditions to select low-toxicity, non-pathogenic variants. These strains are then processed into vaccines. Before distribution, they undergo repeated toxicity and pathogenicity tests to ensure safety. Generally, they are considered safe.

However, attenuated live vaccines carry a risk of allergic reactions in recipients, including anaphylactic shock or even death. Therefore, close monitoring is required after vaccination.

Weighing the risks, anthrax has an extremely high fatality rate. Thus, for high-risk populations, vaccination with the attenuated live anthrax vaccine remains necessary.