Figure 2.

Relationship of number of spores S to which a recipient is exposed and the probability of developing inhalational anthrax, according to age of the recipient. The probabilities are given by the formulas Pr[n](S) = b[n] (exp(S/a[n]) − 1) / (1 + b[n] (exp(S/a[n]) − 1)), n = 1, 2, 3, 4, where the two parameters a[n] and b[n] are determined by the infectious doses that produce infections in 50% (ID₅₀) and 10% (ID₁₀) of exposed persons. The values ID₅₀ and ID₁₀ for the four age brackets are given in Table 3. (A) <25 years. (B) 25–44 years. (C) 45–65 years. (D) >65 years.