Anthrax in Humans: Q&As

What is anthrax?

Anthrax is a bacterial infection caused by the organism Bacillus anthracis. The disease occurs most often in wild and domestic animals in Asia, Africa and parts of Europe; humans are rarely infected. The organism can exist as spores that allow survival in the environment, e.g. in soil, for many years.

How does anthrax affect humans?

There are three usual forms of human disease depending on how infection is acquired: cutaneous (skin), inhalation and ingestion. In over 95% of cases the infection is cutaneous, generally caught by direct contact with the skins or tissues of infected animals. Inhalation anthrax is rare and is caught by breathing in anthrax spores. Intestinal anthrax is very rare, and occurs from ingestion of contaminated meat. In December 2009, a case of ingestion anthrax occurred in the USA in a woman whose exposure appears to have been related to animal skin drums. Since December 2009 a novel form of anthrax has been described in heroin users in Scotland; 'injection anthrax'. The infection is thought to have been aquired from using heroin contaminated by anthrax spores.

All forms of anthrax can lead to an overwhelming infection with anthrax organisms in the blood together with the anthrax toxin, which poisons cells in the body and causes the swelling and inflammation associated with the disease.

How common is anthrax?

Human infections are more frequent in countries where the disease is common in animals, including countries in South and Central America, southern and eastern Europe, Asia and Africa.
The disease used to be known as ‘wool-sorters disease’ and was a recognised occupational hazard for some workers, including woollen mill workers, abattoir workers, tanners, and those who process hides, hair, bone and bone products. However, anthrax is now uncommon in humans in the UK, only a handful of cutaneous cases have been notified over the last decade. A death from anthrax occurred in Scotland in 2006; this was a case of atypical inhalation anthrax which probably followed exposure as a result of playing/handling animal hide drums. Between 1981 and 2009 a total of 19 cases of anthrax were reported in England and Wales; the most recent case occurred in October 2008. This was a fatal case of inhalation anthrax in a man whose exposure occurred during manipulation of animal hides while drum-making.

In December 2009 an outbreak of anthrax started amongst drug users in Scotland, and similar cases were subsequently diagnosed in England during 2010. It is thought that the infection was acquired through use of heroin contaminated with anthrax spores. Anthrax in injecting drug users appears to be very rare; prior to this outbreak only one case had been reported, in Norway in 2000.

How long can you have the infection before developing symptoms?

This is dependent on the dose and route of exposure and may vary from one day to eight weeks. However, symptoms usually develop within 48 hours with inhalation anthrax and 1-7 days with cutaneous anthrax.

What are the symptoms?

Early identification of anthrax can be difficult as the initial symptoms are similar to other illnesses.

Cutaneous anthrax - Local skin involvement after direct contact.

Commonly seen on hands, forearms, head and neck. The lesion is usually single
1-7 days after exposure a raised, itchy, inflamed pimple appears followed by a papule that turns vesicular (into a blister). Extensive oedema or swelling accompanies the lesion – the swelling tends to be much greater than would normally be expected for the size of the lesion and this is usually PAINLESS
The blister then ulcerates and then 2-6 days later the classical black eschar develops
If left untreated the infection can spread to cause blood poisoning

Inhalation anthrax - symptoms begin with a flu-like illness (fever, headache, muscle aches and non-productive cough) followed by severe respiratory difficulties and shock 2-6 days later. Untreated disease is usually fatal, and treatment must be given as soon as possible to reduce mortality.

Intestinal anthrax is contracted by the ingestion of contaminated carcasses and results in severe disease which can be fatal. This is found in some parts of the world where the value of an animal dying unexpectedly outweighs any fears of contracting the disease.

Injection anthrax - the clinical presentation varies according to the way in which the heroin was used and often involves:

Swelling and redness at an injection site, which may or may not be painful
Abscess or ulcer at an injection site often with marked swelling (oedema)
Septicaemia (blood poisoning)

Is a person with anthrax a risk to others?

It is extremely rare for anthrax to be spread from person-to-person. Airborne transmission from one person to another does not occur; there have been one or two reports of spread from skin anthrax but this is very, very rare.

Can anthrax be treated?

Cutaneous anthrax can be readily treated and cured with antibiotics. Mortality is often high with inhalation, injection and gastrointestinal anthrax, since successful treatment depends on early recognition of the disease.

Is there a vaccine?

There is a vaccine against anthrax, and this is recommended only for those at highest risk, for example, those handling dead animals (e.g., abattoir workers, tanners) and laboratory staff who may be handling the organism. Vaccination is not normally recommended for the general public. However, vaccination may be considered as part of the treatment regimen for people who have been exposed to anthrax as it can reduce the length of the antibiotic course required.

For information about anthrax in animals, please see:

Last reviewed: 23 December 2010