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28 February 2019

Causative agent

Anthrax is an acute infectious disease caused by the bacterium Bacillus anthracis. The disease most commonly occurs in animals and can also infect humans.

It is infrequent in most industrialized countries. It is most common in agricultural regions where anthrax in animals is common. In humans, the disease more often affects agriculture and wildlife workers who may handle infected animals. Anthrax is very rare in Hong Kong. There was no case reported in the past 10 years.

Mode of transmission

Anthrax spores can cause infection on entry via skin, gastrointestinal or respiratory tract. For example, they may enter the body through abraded skin, get swallowed, or inhaled as a fine, aerosolised mist.

Transmission from person to person is very rare.

Incubation period

Symptoms vary depending on how the disease is contracted. Symptoms usually occur 1 to 7 days after exposure, but the incubation period can be more than 2 months.

Clinical features

Cutaneous anthrax: It begins as an itchy papule which later develops into a painless ulcer with a black centre. There may be fever, headache, muscle ache, vomiting and regional lymphadenopathy. The disease can be readily cured with appropriate treatment.

Inhalation anthrax: It is the most severe form of anthrax. Initial symptoms resemble a common cold but then rapidly progress to severe breathing problems and shock. Inhalation anthrax without early treatment is usually fatal.

Intestinal anthrax: Initial symptoms include nausea, loss of appetite, vomiting, abdominal pain, fever, and severe diarrhoea. Intestinal anthrax can be fatal without early treatment.


Anthrax can be treated with antibiotics. The disease may be prevented after exposure to anthrax spores by early treatment with appropriate antibiotics.


  1. Maintain good personal, food and environmental hygiene.
  2. Perform hand hygiene frequently, wash hands thoroughly with liquid soap and water before handling food or eating.
  3. Clean the broken skin immediately and cover properly with waterproof adhesive dressings. Wash hands before and after touching wounds.
  4. Avoid contact with infected animal and contaminated animal product.
  5. Thorough washing and cooking of food before consumption.