Outbreak of Norovirus Associated with Gulf Coast Oysters, TN, 2009

Sarah Hill and Margaret Zylstra

Tennessee Department of Health, Chattanooga-Hamilton County Health Department

Norovirus

• Common

• Low infectious dose

• Human fecal pathogen

• Contaminates fresh and marine waters

• Environmentally stable

• Not the reservoir for norovirus

• Filter water over gills and mantle, 5 L/h

• Viruses and bacteria

• Frequently consumed raw

Public Health Investigation

• Outbreak?– 3/9, 3 ill persons call CHR report eating raw

oysters at Restaurant A

• Environmental investigation– Facility inspected– Score of 83, one critical violation

• Chicken salad holding at 45° F rather than <41° F• All oyster storage and serving was adequate

– Raw oysters (n=24) and tags collected from restaurant

Investigation Results

• Case definition: Person who developed vomiting and/or diarrhea within 3 days of eating at Restaurant A 3/5-3/7

• 13 ill identified and 30 controls enrolled• 4 confirmed norovirus genogroup 1• Cases from TN, AL, GA, MO• No ill restaurant staff

• Oysters: negative for norovirus

Onset of Illness following consumption of MS A2C oysters

0

1

2

3

4

5

6

7

8

9

10

3/4 3/5 3/6 3/7 3/8 3/9

Onset date

Nu

mb

er il

l

A2C oysters consumed at Restaurant A

Food OR 95% CI P value

Raw Oysters 108 10-1147 <0.0001

Fried Oysters 0.5 0.1-5.4 0.6

Fire-roasted Oysters

0.1 0-1.8 0.04

Salad 1.2 0.3-5.1 0.8

Other entrée 0.1 0-0.4 0.0007

Actions

• 3/14 CHR and Tennessee DOH inform FDA of epi association

• Mississippi Dept of Marine Resources – 3/17 closed harvest area– Recalled 2/24 harvest– Recommended cooking oysters harvested 2/25-

3/17

• Tennessee (3/20) and FDA (3/21) advised consumers to avoid oysters harvested 2/25-3/17

Discussion

• Surveillance and rapid investigation, cooperation of Restaurant A key

• Epi data v. lab data

• Mississippi investigating illness reports

• Mississippi Dept of Marine Resources has requested FDA assistance to evaluate potential sources of contamination

Questions?

Tennessee Department of HealthCommunicable and Environmental Diseases1st Floor, Cordell Hull Building425 5th Avenue NorthNashville, TN 3724615.741.7247