Bacillus anthracis

Hosts

This bacterium infects multiple types of hosts including herbivorous mammals such as livestock and is considered zoonotic however humans are a dead end host and do not become infectious

Transmission / Exposure Route

Cutaneous: skin contact with spores from infected animals (95% of Cases; Most in Africa, Asia, and eastern Europe).
Gastrointestinal: eating poorly cooked meat/dairy from infected animal. 
Inhalation: Inhalation of spores
Injectional: soft tissue infection associated with injection drug use [1] 
Anthrax is not contagious and cannot be transmitted from person-to-person. [2]

Burden Of Disease

Duration of infectiousness and disease
Gastrointestinal: 10-14 days[1]

Symptomology
Cutaneous: 
Primary skin lesion 3-5 days after infection is painless puriritic papule.
Lesion forms a necrotic vesicle leaving a black eschar surrounded by edma.
Eschar dries and sloughs in next 1-2 weeks.

Gastrointestinal: 
Oral-pharyngeal form: oral or esophageal ulcer with regional lymphadenopathy edema and sepsis
Lower GI form: primary intestinal lesions predominantly in terminal ileum or cecum. Nausea, vomiting, malaise, bloody diarrhea, acute abdomen, and sepsis are common symptoms of the Lower GI form.

Inhalational: 
Two-stages

1. Flu-like symptoms including cough fever, fatigue that last from hours to a few days
2. Rising fever, dyspnea, diaphoresis, shock. In advanced form, cyanosis and hypotension progress rapidly and death can occur within hours

Injectional: 
Tissue swelling around the injection site
Abdominal symptoms[1]

Excretion Rates (see Exposure)
Spores are cleared from the lung at a rate between 8-14% per day. [2]

Immunity
Anthrax vaccination consists of 5 total intramuscular injections, followed by recommended annual boosters to maintain immunity. [3]

Incubation Period

Cutaneous: 0-1 day. Other forms: 1-7 days, rarely up to 60 days (CDC)

Microbiology

Gram +, aerobic, encapsulated, nonmotile. Exists in a dormant spore or an actively replicating vegetative rod form Extremely hardy spores can persist for years, even decades.[1]