Skip to main content
hpa logo
Topics A-Z:
Search the site:
Home › Topics › Infectious Diseases › Infections A-Z › Anthrax (Deliberate Releases) ›Guidance ›  Clinical Features of Disease
Printer friendly page (opens in new window)

Clinical Features of Disease

Forms of disease

Human anthrax can occur in four forms: inhalation/pulmonary, cutaneous, gastrointestinal, or injection anthrax depending on the route of exposure, and details of these diseases are given below. It can be expected that any malicious or deliberate release of anthrax spores will involve aerosol exposure.

Clinicians should be aware of the possibility of cases of inhalation anthrax, and any previously healthy patient with the following clinical presentations should be immediately reported to the Consultant in Communicable Disease Control at the local Helath Protection Unit and to the 24 hour duty doctor at HPA Colindale (020 8200 6868).

  • Rapid onset of severe, unexplained febrile illness or febrile death.
  • Rapid onset of severe sepsis not due to a predisposing illness, or respiratory failure with a widened mediastinum.
  • Severe sepsis with Gram-positive rods or Bacillus species identified in the blood or cerebrospinal fluid and assessed not to be a contaminant.

See clinical pictures illustrating the different forms of anthrax infection.

Inhalation/pulmonary anthrax

  • Following inhalation of spores, there is a non-specific prodrome of flu-like illness ( fever, headache, myalgia and non-productive cough). Symptoms more often associated with inhalation anthrax than other flu-like illness include: nausea, vomiting, pallor or cyanosis, sweating, altered mental status and raised red blood cell count.
  • Two to four days after initial symptoms, there is abrupt onset of respiratory failure and on chest X-ray a widened mediastinum is often present, suggestive of mediastinal lymphadenopathy and haemorrhagic mediastinitis. The most accurate predictor of inhalation anthrax cases was mediastinal widening or pleural effusions. Note that a widened mediastinum may also be apparent in cases of TB due mediastinal lymphadenopathy.
  • Gram-positive bacilli seen in blood cultures (if taken before antibiotic treatment), usually after 2-3 days of onset of illness.
  • Treatment may be successful in the prodromal stage, but by the time respiratory or bacteraemic symptoms develop, treatment may not arrest the disease before a fatal outcome.
  • See algorithm for clinical evaluation and management of inhalation anthrax

Cutaneous anthrax

  • Local skin involvement after direct contact.
  • Commonly seen on hands, forearms, head and neck.
  • Three days after exposure a raised, itchy, inflamed pimple appears followed by a papule that turns vesicular. Extensive oedema 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. Then 2-6 days later the classical black eschar develops.
  • Responds to oral antibiotics.
  • Rarely may progress to bacteraemia or meningitis without treatment.
  • See algorithm for clinical evaluation and management of cutaneous anthrax 

Gastro-intestinal

  • Rare - there are two forms abdominal and oropharyngeal (this is even less common).
  • Characterised by severe abdominal pain, loss of appetite, malaise, fever, nausea and vomiting with watery or bloody diarrhoea.
  • Bacteraemia may develop 2-3 days after onset.
  • Usually fatal if it progresses to bacteraemia.

Injection Anthrax

A novel form of anthrax has recently been recognised. Since December 2009, drug users in Scotland, England and Germany have been found to have acquired anthrax through using heroin contaminated with anthrax spores (Ramsay et al 2010). Users have frequently but not exclusively been injectors (Booth et al 2010). Follow the link for the latest information in England and links to information in Scotland.

This type of anthrax had only reported once before, in Norway in 2000. Cases in the UK have presented in a variety of ways:

  • Severe soft tissue infection, including necrotizing fascitis and cellulitis/ abscess, particularly if associated with oedema which is often marked. Compartment syndrome has also been noted.
  • Signs of severe sepsis, with or without evidence of soft tissue infection.
  • Meningitis (especially haemorrhagic meningitis) including clinical and/or CT evidence suggestive of subarachnoid haemorrhage or intracranial bleed.
  • Gastrointestinal symptoms - abdominal pain, nausea, vomiting, diarrhoea, GI haemorrhage.
  • Algorithm for clinical evaluation and management of drug users with possible anthrax

Mortality

Systemic infection resulting from inhalation of the organism has a mortality rate approaching 100%, with death usually occurring within a few days after the onset of symptoms. Cutaneous anthrax, the most common form, is usually curable with antibiotics (less than 1% fatality). The mortality rate among people with infection resulting from ingestion is variable, but may also approach 100%. There has been a 33% case fatality rate amongst the 52 cases of injection anthrax reported in the UK between December 2009 and December 2010.

Antimicrobial susceptibilities

Most naturally occurring anthrax strains are sensitive to penicillin, which historically has been the preferred therapy for the treatment of anthrax. However, the deliberate release of anthrax spores in the US in 2001 and the subsequent experience of treating patients with inhalation and cutaneous anthrax has led to the CDC issuing revised guidance on treatment and prophylaxis - this is available from their website at http://www.bt.cdc.gov/agent/anthrax/treatment/index.asp

Ciprofloxacin or doxycycline should be considered an essential part of the first-line therapy for inhalation anthrax. Due to concerns about constitutive and inducible beta-lactamases in B. anthracis, penicillin and ampicillin should not be used alone for the treatment of inhalation anthrax.


Last reviewed: 23 December 2010