Anthrax Fact Sheet
What is Anthrax?
Anthrax, an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis, most commonly occurs in hoofed mammals and can also infect humans. It is a widespread zoonosis transmitted from domestic animals (cattle, sheep, goats, buffaloes, pigs and others) to humans by direct contact or through animal products. Human anthrax is a serious problem in several countries and has potential for explosive outbreaks (especially the gastro-intestinal form); while pulmonary (inhalation) anthrax is mainly occupational, the threat of biological warfare attacks should not be forgotten. Anthrax has a serious impact on the trade of animal products. The control of anthrax is based on its prevention in livestock: programs based only on prevention in humans are costly and likely to be ineffective except for those industrially exposed. There is an effective vaccine for those occupationally exposed, and successful vaccines for livestock, particularly for herds with ongoing exposure to contaminated soil. In most countries anthrax is a notifiable disease. Surveillance is important to monitor the control programs and to detect outbreaks.
Symptoms
Symptoms of disease vary depending on how the disease was contracted, but usually occur within 7 days after exposure. The serious forms of human anthrax are inhalation anthrax, cutaneous anthrax, and intestinal anthrax. Initial symptoms of inhalation anthrax infection may resemble a common cold. After several days, the symptoms may progress to severe breathing problems and shock. Inhalation anthrax is often fatal. The intestinal disease form of anthrax may follow the consumption of contaminated food and is characterized 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 diarrhea.
Spread
Direct person-to-person spread of anthrax is extremely unlikely, if it occurs at all. Therefore, there is no need to immunize or treat contacts of persons ill with anthrax, such as household contacts, friends, or coworkers, unless they also were also exposed to the same source of infection.
Treatment
In persons exposed to anthrax, infection can be prevented with antibiotic treatment. Early antibiotic treatment of anthrax is essential-delay lessens chances for survival. Anthrax usually is susceptible to penicillin, doxycycline, and fluoroquinolones. An anthrax vaccine also can prevent infection. Vaccination against anthrax is not recommended for the general public to prevent disease and is not available.
Recommended case definition
Clinical description
An illness with acute onset characterized by several clinical forms. These are:
- localized form: (more frequent)
- cutaneous: skin lesion evolving over 2 to 6 days from a papular through a vesicular stage, to a depressed black eschar invariably accompanied by edema that may be mild to extensive.
- systemic forms: (sporadic)
- gastro-intestinal: abdominal distress characterized by nausea, vomiting, anorexia and followed by fever.
- pulmonary (inhalation): brief prodrome resembling acute viral respiratory illness, followed by rapid onset of hypoxia, dyspnoea and high temperature, with X-ray evidence of mediastinal widening.
- meningeal: acute onset of high fever possibly with convulsions, loss of consciousness, meningeal signs and symptoms; commonly noted in all systemic infections.
Laboratory criteria for diagnosis
Laboratory confirmation by one or more of the following:
- Isolation of Bacillus anthracis from a clinical specimen (e.g., blood, lesions, discharges).
- Demonstration of B. anthracis in a clinical specimen by microscopic examination of stained smears (vesicular fluid, blood, cerebrospinal fluid, pleural fluid, stools).
- Positive serology (ELISA, Western blot, toxin detection, chromatographic assay, fluorescent antibody test (FAT)). Note: It may be not possible to demonstrate B. anthracis in clinical specimens if the patient has been treated with antimicrobial agents.
Case classification
Suspected: A case that is compatible with the clinical description and has an epidemiological link to confirmed or suspected animal cases or contaminated animal products.
Probable: A suspected case that has a positive reaction to allergic skin test (in non-vaccinated individuals).
Confirmed: A suspected case that is laboratory-confirmed.
Recommended types of surveillance
Since the usual ratio of livestock cases to human cases is of the order of 10-20:1, it is ineffective to depend only on human case reports. Routine surveillance must be undertaken, especially in high-risk groups (slaughterhouse workers, shepherds, veterinarians, wool/hide workers), and unexplained sudden livestock deaths must be investigated. Mandatory immediate case-based reporting from peripheral level (health care providers or laboratory) to intermediate and central levels of public health sector and to the appropriate level of animal health sector. All cases must be investigated.
Routine monthly reporting of aggregated data on confirmed cases and investigation reports from intermediate to central level in public health and animal health sectors.
Recommended minimum data elements
Case-based data for investigation and reporting:
- Case classification by type (suspected / probable / confirmed), and by clinical form (cutaneous / gastro-intestinal / pulmonary (inhalation) / meningeal)
- Unique identifier, age, sex, geographical information, occupation
- Date of onset, date of reporting
- Exposure history
- Outcome.
Aggregated data for reporting to central level:
- Number of confirmed cases by age, sex, clinical form (cutaneous / gastro-intestinal / pulmonary (inhalation) / meningeal).
- Similarly for livestock by outbreaks and cases in relation to species and appropriate geographic / administrative area.
Principal uses of data for decision-making
Surveillance data
- Estimate the magnitude of the problem in humans and animals
- Monitor the distribution and spread of the disease in humans and animals
- Detect outbreaks in humans and animals
- Monitor and evaluate the impact of prevention activities in humans and of control measures in animals
Investigation data
- Identify populations at risk
- Identify potentially contaminated products of animal origin
- Identify potentially contaminated animal sources (herds or flocks)
PAHO, which was founded in 1902, works with all the countries of the Americas to improve the health and raise the living standards of their peoples, and serves as the Regional Office for the Americas of the World Health Organization.
For more information, please contact: Daniel Epstein, Office of Public Information, (202) 974-3459, epsteind@paho.org
