- The disease
- Reason for surveillance
- Case definition
- Notification criteria and procedure
- Managing single notifications
- Managing special situations
- Additional resources
1. The disease
Bacillus anthracis, a bacterium.
Mode of transmission
Anthrax is acquired in three ways: percutaneously, by inhalation, or by ingestion. B. anthracis spores can remain viable in soil for many years. Humans can become infected with anthrax by handling products from infected animals, by inhaling anthrax spores (especially from contaminated animal products such as hides) or through cuts and abrasions when in contact with contaminated soil. Eating undercooked meat from infected animals can also transmit anthrax. Transmission from person to person has not been reported. Articles and soil contaminated with spores may remain infective for decades. Whilst several cases are reported each year among sheep and other domestic animals mainly in the west of New South Wales (NSW), human cases rarely occur in NSW. In 2001, several people in the USA contracted anthrax from spores maliciously distributed through the mail.
Symptoms can appear within seven days of coming in contact with the bacterium for all three types of anthrax although incubation periods of up to 60 days are possible. The reported incubation period for cutaneous anthrax ranges from three to ten days (commonly five to seven days). The incubation period for gastrointestinal anthrax is suspected to be three to seven days and respiratory incubation for anthrax has been reported from one to 60 days (commonly one to five days).
The symptoms of the disease vary depending on how the disease was contracted.
About 95 per cent of reported anthrax infections occur when the bacterium (or spore) enters a cut or abrasion on the skin, (eg. when handling contaminated wool, hides, leather or hair products of infected animals). Skin infection begins as a small papule and progresses to a vesicle in one to two days. The vesicle then erodes, leaving a necrotic ulcer with a characteristic black centre. Secondary vesicles are sometimes observed. The lesion is usually painless. Other symptoms can include swelling of adjacent lymph glands, fever, malaise and headache. The case fatality rate of cutaneous anthrax can be up to 20 per cent without antibiotic treatment and <1 per cent with antibiotic treatment.
Initial symptoms may resemble an influenza-like illness (ILI), which include a sore throat, mild fever and myalgia in the absence of rhinorrhoea. This prodromal phase is characteristically followed by partial resolution of symptoms followed after several days by rapid progression to severe breathing problems and shock. The cardinal feature is a widening mediastinum on chest X-ray without pulmonary infiltrates. Meningitis frequently occurs. Inhalation anthrax is usually fatal even when treated, but commencement of antibiotics during the prodrome may be effective.
The gastrointestinal form of anthrax usually occurs after eating contaminated meat and is characterised by an acute inflammation of the intestinal tract. Initial signs of nausea, loss of appetite, vomiting, and fever are followed by abdominal pain, vomiting of blood and severe diarrhoea. Gastrointestinal anthrax results in death in 25% to 60% of cases.
2. Reason for surveillance
- To identify and protect persons at risk of infection, and identify the source of infection (whether natural or deliberate)
- To monitor the epidemiology of anthrax and so inform the development of better prevention strategies.
3. Case definition
A confirmed case requires either:
- laboratory definitive evidence, or
- laboratory suggestive evidence and clinical evidence.
Laboratory definitive evidence
Isolation of Bacillus anthracis-like organisms or spores confirmed by a reference laboratory.
Laboratory suggestive evidence
- Detection of B. anthracis by microscopic examination of stained smears, or
- detection of B. anthracis by nucleic acid test (NAT, e.g. PCR).
- Cutaneous: skin lesion evolving over 1-6 days from a papular through a vesicular stage, to a depressed black eschar invariably accompanied by oedema that may be mild to extensive, or
- Gastrointestinal: abdominal distress characterised by nausea, vomiting, anorexia and followed by fever, or
- Inhalational: rapid onset of hypoxia, dyspnoea and high temperature, with radiological evidence of mediastinal widening, or
- Meningeal: acute onset of high fever, convulsions, loss of consciousness, and meningeal signs and symptoms.
4. Notification criteria and procedure
Anthrax is to be immediately notified by laboratories on suggestive or definitive laboratory evidence (ideally by telephone). Confirmed cases should be entered onto NCIMS.
5. Managing single notifications
On same day of notification begin follow-up investigation, and notify CDB of case details.
Within one working day of notification enter confirmed cases on NCIMS.
The response to a notification will normally be carried out in collaboration with the case's health carers, but regardless of who does the follow-up PHU staff should ensure that action has been taken to:
- identify likely source of infection (whether natural or deliberate)
- confirm the onset date and symptoms of the illness
- confirm results of relevant pathology tests, or recommend the tests be done
- find out if the case or relevant care-giver has been told what the diagnosis is before interviewing them
- seek the doctor's permission to contact the case or relevant care-giver
- review case management.
Investigation and treatment
For treatment recommendations, see Therapeutic Guidelines: Antibiotic.
Obtain a history of exposure to infected animals or animal products (e.g. contaminated hair, wool, hides, or products made from them), or anthrax vaccines and trace to the place of origin. In a manufacturing plant, inspect for adequacy of preventative measures. Consider the possibility that the infection arose from deliberate exposure.
In the event of a human case occurring in a person in contact with animals or animal products, the local Department of Primary Industries Veterinary Officer should be informed on the same day.
Where an occupational or other exposure risk factor cannot be identified, consideration should be given to broadening the investigation in consultation with CDB and Reference Laboratories to assist with typing of the organism.
Isolation and restriction
Although the lesion is likely to be sterile after 24 hours treatment, dressings soiled with discharges from lesions should be burned and reusable surgical equipment must be sterilised. Standard infection control precautions apply for all direct clinical care.
The case or relevant caregiver should be informed about the nature of the infection and the mode of transmission. In particular, emphasis should be placed on careful handling of soiled dressings and contaminated clothing. Education on the handling of carcasses and products of potentially infected animals should be a priority.
Identify the likely source of infection in conjunction with the Department of Primary Industries, who may initiate animal control measures.
Identification of contacts
Contacts are those who may have been exposed to the same source as the case.
Control of human contacts with infectious animals/materials
- Public Health Units should liaise with Department of Primary Industries to ensure that all people potentially at risk are provided with information about the disease, including symptoms and decontamination procedures where relevant.
- Contacts should be informed about anthrax and symptoms associated with cutaneous and inhalation disease, and advised to seek medical attention if they develop an illness consistent with anthrax.
- Where inhalational exposure to a deliberate release of anthrax spores is considered credible, then recommend post exposure prophylaxis (see Therapeutic Guidelines: Antibiotic) and seek expert medical advice.
- Post exposure prophylaxis for cutaneous anthrax should be considered for contacts of a confirmed anthrax exposure who were not using personal protective equipment and whose skin was contaminated with fluids from the carcass. The presence of abrasions on the skin would further support chemoprophylaxis. In this setting, a short course of antibiotics (usually 10 days) may be recommended rather than the 60 day course usually recommended following an inhalational exposure to deliberately released anthrax spores.
An anthrax vaccine is not licensed for civilian use in Australia.
Decontamination of clothing and equipment
- All personnel handling potentially contaminated materials should wear gloves and protective clothing and ensure that skin breaks are protected with sealed waterproof dressings. Additional protection such as respiratory masks is NOT required. All personnel should be instructed to shower thoroughly with soap and water.
- Contaminated clothing and items should be minimally handled (to avoid agitation) and stored in labelled double plastic bags until exposure to anthrax has been excluded.
- Material/equipment that requires decontamination following confirmation of anthrax should be either incinerated or sterilized at 121°C for 30 minutes. If this is not possible then liaise with NSW Department of Primary Industries regarding decontamination procedures using chemical disinfectants.
- The Chief Veterinary Officer will determine the method/s of decontamination of a site, facility or any heavy equipment at risk of being contaminated with B. anthracis.
- For information on disposal of infected animals and animal by-products refer to the AUSVET Plan Disease Strategy Anthrax
- For procedures following a laboratory accident refer to Guidelines for the Surveillance and Control of Anthrax in Humans and Animals WHO/EMC/ZDI/98/6
6. Managing special situations
Where a person has been exposed to a suspicious substance, he or she should be advised to call 000 so that NSW Police can assess the incident.
Where an incident is deemed 'high risk' by NSW Police due to an actual threat to the health or safety of high profile or other persons as a result of deliberate exposure to a suspicious substance, Forensic Service specialist may attend the incident scene and collect environmental samples for testing.
The Chief Health Officer will be notified of any samples that test positive for anthrax and will inform the local Public Health Unit (PHU).
While efforts are made to adhere to this chain of communication, notification of a positive anthrax result may reach the PHU through different channels. Regardless, the PHU must ensure that both the Chief Health Officer and LHD Health Services Functional Area Coordinator (HSFAC) have been notified.
It is important to recognise that low to medium risk suspicious substance (white powder) incidents (sometimes known as "white powder" incidents) occur relatively frequently and that in most situations notification to public health will not be required.
Public health action
A preliminary or definitive finding of anthrax (preliminary or definitive) in an environmental sample to which people have been potentially exposed will prompt the State Public Health Controller to initiate an urgent meeting involving officials from NSW Ministry of Health, Health Protection NSW, and the local PHU. This meeting may also include infectious diseases specialists and laboratory experts.
The aims of the meeting will be: to assess the risk to exposed people and to determine whether interventions such as antibiotic prophylaxis and symptom monitoring will be recommended for them, and; to determine if any further public health actions or investigations are required, subject to advice from NSW Police.
The local PHU may be tasked with managing contacts identified by NSW Police as having been exposed to material that tested positive for anthrax. This will involve informing them of the results, counselling them about the risk and, if recommended, arrange for antibiotic prophylaxis and symptom monitoring. Contact details for exposed people will be usually be accessed from NSW Police via the State HSFAC and State Public Health Controller.
7. Additional resources