Volume 22, Number 12—December 2016
Research
Infectious Dose of Listeria monocytogenes in Outbreak Linked to Ice Cream, United States, 2015
Table 2
Probability of invasive listeriosis after ingestion of ice cream products contaminated with Listeria monocytogenes, United States, 2015
Exposure scenario/model | Population, no. cases in population |
||||
---|---|---|---|---|---|
All, n = 4 | Highly susceptible, n = 4 | Pregnant, n = 0* | Age >65 y, n = 4 | Age >75 y, n = 2 | |
Lower† | |||||
r Constant | |||||
No. L. monocytogenes cells consumed | 1.5 × 109 | 7.2 × 106 | 2.2 × 107 | 2.3 × 108 | 1.2 × 108 |
Estimated r parameter | 2.6 × 10−9 | 5.5 × 10−7 | <2.3 × 10−8 | 1.7 × 10−8 | 1.7 × 10−8 |
Corresponding to 1 case every … servings‡ | 37,867 | 181 | >4,363 | 5,756 | 5,832 |
Log10(r) normally distributed | |||||
Estimated μ parameter | −9.38 | −6.19 | <(−7.92) | −8.00 | −8.02 |
Estimated σ parameter |
0.88 |
0.24 |
0.54 |
0.54 |
0.54 |
Medium§ | |||||
r Constant | |||||
No. L. monocytogenes cells consumed | 6.2 × 109 | 1.5 × 107 | 8.9 × 107 | 9.4 × 108 | 4.8 × 108 |
Estimated r parameter | 6.5 × 10−10 | 2.7 × 10−7 | <5.6 × 10−9 | 4.3 × 10−9 | 4.2 × 10−9 |
Corresponding to 1 case every … servings‡ | 154,612 | 375 | >17,812 | 23,501 | 23,811 |
Log10(r) normally distributed | |||||
Estimated μ parameter | −10.0 | −6.40 | <(−8.49) | −8.60 | −8.62 |
Estimated σ parameter |
0.88 |
0.24 |
0.54 |
0.54 |
0.54 |
High¶ | |||||
r Constant | |||||
No. L. monocytogenes cells consumed | 1.4 × 1010 | 3.3 × 107 | 2.0 × 108 | 2.1 × 109 | 1.0 × 109 |
Estimated r parameter | 2.9 × 10−10 | 1.2 × 10−7 | <2.6 × 10−9 | 1.9 × 10−9 | 1.9 × 10−9 |
Corresponding to 1 case every … servings‡ | 339,153 | 816 | >39,071 | 51,552 | 52,230 |
Log10(r) normally distributed | |||||
Estimated μ parameter | −10.3 | −6.80 | <(−8.83) | −8.97 | −8.97 |
Estimated σ parameter | 0.88 | 0.24 | 0.54 | 0.54 | 0.54 |
*0.5 used for computation.
†Products 1–3 contaminated beginning 2013 Dec 1; products 4–8 not contaminated.
‡Corresponding to 1 case every … servings, Including 10,000 L. monocytogenes cells.
§Products 1–8 contaminated beginning 2013 Dec 1.
¶Products 1–8 contaminated beginning 2012 Jun 1.