Research Article
Listeriosis Outbreaks in British Columbia, Canada, Caused by Soft Ripened Cheese Contaminated from Environmental Sources
Table 1
Summary of outbreak findings.
| | | Outbreak A | Outbreak B |
| | Illnesses | | | | Total number of illnesses | 49 | 86 | | First reported illness | February 3, 2002 | August 15, 2002 | | Organism identified | L.m. | L.m. | | Serotype | 4b | 4b | | PFGE designations—Apa I | LMAAI.0140 | LMAAI.0017 | | —Asc I | LMACI.0023 | LMACI.0082 | | Number of noninvasive (clinical) cases | | | | Febrile gastroenteritis (stool+) | 44 (6) | 86 (14) | | Number of invasive (confirmed) cases | | | | Meningitis | 3 | 0 | | Bacteremia in pregnancy | 2 | 0 | | Demographics | | | | Age range in years (median) | 4 to 85 (49) | 14 to 76 (46) | | % Female | 64 | 72 | | Clinical findings | | | | Incubation period in days (median) | 1 to 33 (7) | 0.5 to 28 (2) | | Symptoms reported (%) | | | | Fatigue | 51 | 62 | | Myalgia | 46 | 55 | | Chills | 38 | 0 | | Night sweats | 24 | 0 | | Bone pain | 19 | 0 | | Abdominal pain | 8 | 54 | | Cheese1 prepared at plant | | | | Number of cheese types produced | 14 | 10+ | | Bacterial smear surface soft ripened cheese | | Yes | | Chevre (goat milk soft cheese) | | No | | Curds (e.g., cheddar) | | Yes | | Feta cheese | Yes | Yes | | Soft cheese (e.g., fromage frais) | Yes | Yes | | Hard cheese (e.g., cheddar cheese) | | Yes | | Semihard cheese (e.g., raclette) | No | | | Soft mould ripened cheese | | | | Investigation findings (Acceptable/neutral/unacceptable) | | | | Raw milk quality and handling | Acceptable | Acceptable | | Pasteurization effectiveness/procedures | Acceptable | Acceptable | | Pasteurization equipment | Acceptable | Acceptable | | Postpasteurization—raw milk contamination | Neutral | Acceptable | | Postpasteurization—interior plant environment | Acceptable | Acceptable | | Postpasteurization—ingredients | Unacceptable | Unacceptable | | Postpasteurization—personnel | Unacceptable | Acceptable | | External environment | Neutral | Unacceptable |
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Cheese types made with cow or goat milk unless specified; cheese products linked to illness are indicated in bold with; L.m., Listeria monocyotogenes.
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