Estimating the Attack Rate of Pregnancy-Associated Listeriosis during a Large Outbreak

Table 1

Attack rates of listeriosis among pregnant women exposed to contaminated cantaloupe, estimated using three methods, Colorado, 2011.

Method (equation)^a	Pregnancy-associated listeriosis	Estimated exposed women^b	Estimated attack rate; (per 10,000 exposed pregnant women)
(1) Colorado cantaloupe distributed nationally (3)	1	6,500	1.5
(2) Grocery store chains (4)	1	12,000	0.9
(3) Pregnant residents and cantaloupe consumption (5)	1	7,200	1.4

See Section 2.4 for explanations and equations.
^bCalculated using unrounded estimates; results rounded to two significant figures.