ANTHRAX CASE STUDY (KEY)

DESCRIPTIVE EPIDEMIOLOGY

(A) The Aug. 17, 2001 issue of MMWR reported on a case of human anthrax associated with an epizootic (epidemic) among livestock. The case was a 67-year-old resident of eastern North Dakota who had participated in the disposal of five cows that had died of anthrax. On the day of disposal, he placed chains around the heads and hooves of the animals and moved them to a burial site. This emphasized the importance of increased vigilance for human cases of anthrax during and following outbreaks of anthrax among livestock (Source: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5032a1.htm ).

(B) Before 2000, there hadn't been a human case of anthrax since 1992 (see Editor's note in the above site MMWR link).

(C) Yes, the current cases are alarming in several respects. First, the proximity to the September 11th event make it highly suspicious. Second, seven cases is more than expected, under any circumstance. Third, this may represent the tip of the iceberg. This is clearly an epidemiologic emergency.

AGENT AND RESERVOIR

(D) The agent is a gram-positive encapsulating bacteria (non-motile rod) called Bacillus anthracis.

(E) Anthrax is a zoonotic disease. The normal reservoir for anthrax is animals, mostly herbivores.

(F) The [unnatural] reservoir of bioterrorism-related anthrax [where the agent is multiplied and is stored] is a laboratory.

(G) Environmental cleanup is difficult. Hypochlorite is sporicidal when organic matter is not overwhelming and the item is not corrodible. Spores require steam sterilization, autoclaving or burning to assure complete destruction. Fumigation and chemical disinfection may be effective.

PORTALS AND TRANSMISSION

(H) The Communicable Disease Manual says "transmission from person-to-person is very rare." Any such risk is trivial compared with direct exposure to the mail.

(I) Precautions when handling potentially contaminated materials:

• For cutaneous exposures, people should wear gloves and wash hands after handling potentially contaminated materials. High risk situations also require use of protective clothing. Change, wash, and dispose of protective garments as needed.
• For respiratory form, users should wear inhalation masks.
• For gastrointestinal form, it is important to prevent ingestion of contaminated materials.

(J) In this atypical mode of bioterrorism with of exposure, the fly would be acting as a mechanical vector.

IMMUNITY & TREATMENT

(K) The incubation period is a few hours to several days (usually less than 48 hours).

(L) Untreated cutaneous anthrax has a fatality rate of between 5 and 20 percent. With effective treatment, few deaths occur.

(M) No figure is given for the fatality rate associated with respiratory anthrax. However, the Communicable Disease Manual notes that fever and shock follow acute symptoms in 3 - 5 days with death shortly thereafter. This implies that death is common, if not universal.

(N) The risks probably outweigh the benefits. (This could change in the event of a generalize anthrax attack.)

PREVENTIVE MEASURES

(O) Strategies for prevention may be directed against any of the following infectious disease process:

• Agent. The agent must be detected and neutralized as early as possible. Contaminated environments must be cleaned and disinfection. Decontamination procedures must address cleanup of resistant spore. (Methods of spore deactivation are described in the Communicable Disease Manual.) Contaminated soil must be buried.
• Reservoir. In the case of bioterrorism, the reservoir is military and terrorist labs. The "war on terrorism" is actually a war on the reservoir of terrorism.
• Portals. People who handle contaminated materials should wear inhalation masks and gloves when handling potentially contaminated materials.
• Modes of transmission. Avoid direct contact with skin and avoid aerosolized agent.
• Immunity. Cases often recover from cutaneous anthrax, especially with effective treatment. But respiratory anthrax is often if not universally fatal. An effective pre-exposure vaccine exists, but its use is restricted to individuals at "calculable risk" (e.g., certain military personnel, laboratory workers). Prophylactic treatment of exposed people with antibiotics may be effective. Educating employees who handle potentially contaminated articles about the modes of transmission is important in helping them avoid exposure and take care of skin abrasions and personal cleanliness.