Case Definitions

Suspected cases

Any previously healthy patient with the following clinical presentations should be immediately reported to the Consultant in Communicable Disease Control at the local Health Protection Unit and to the duty doctor at HPA Colindale (020 8200 6868 - 24 hour service).

• 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.

If anthrax is suspected, microbiological specimens should be sent to the reference laboratory, and consideration should be given to initiating empirical treatment pending results. Obviously the level of suspicion of anthrax depends on local circumstances at the time - in the event of a known or suspected deliberate release the threshold for making a diagnosis of anthrax should be lower.

Clinical microbiology laboratories should also be alert to the possibility of anthrax. All sterile site Bacillus isolates should be carefully evaluated, and if suspicious, and/or if the clinical syndrome is suggestive of anthrax, they should be immediately referred to reference laboratory.

Confirmed case

A case that clinically fits the criteria for suspected anthrax, and in addition, definitive positive results are obtained on one or more pathological specimens by the reference laboratory.

Definitive diagnosis in the reference laboratory

The definitive test for B. anthracis is polymerase chain reaction (PCR). This test can be applied to cultures sent from local laboratories, in which case results will be available in three hours from receipt of specimen. It can also be applied to isolates and other clinical samples, but this will normally require overnight culture at the reference laboratory, so the result will take 24 hours.

Last reviewed: 24 December 2010