Minnesota Department of Health (MDH) Bug Bytes

January 25, 2002
Vol. 3: No. 2

Topics in this Issue:

1. Foodborne Outbreak Close to Home
2 . Unexplained Deaths and Critical Illnesses
3. Lyme Disease
4. Influenza Update

1. Foodborne Outbreak Close to Home
MDH employees have a greater appreciation for the impact of foodborne disease and foodborne outbreaks due to recent experience. On January 10, over 110 employees attended an all day seminar on health risk communication (an ironic topic). On January 16, after two MDH infectious disease epidemiologists who had attended the seminar, mentioned they had been "the sickest they had ever been in their life" with vomiting and diarrhea beginning 36 hours after the seminar, we began an investigation. Thirty-two (32%) of 101 interviewed seminar participants met an epidemiologic case definition for gastroenteritis; 25 reported diarrhea, 23 reported stomach cramps, 22 reported vomiting, and 14 reported fever. The median incubation period for illness was 32 hours (range, 22-54 hours) and median duration of illness was 37 hours. Based on these clinical and epidemiologic characteristics, we classified this as an outbreak due to Norwalk-like virus (NLV). Four stool samples were collected for laboratory analysis; 3 tested positive by PCR in our lab for calicivirus (NLVs are in the family Caliciviridae).

Box lunches were served at the seminar. Illness was strongly associated with consumption of coleslaw from the box lunch. All ill persons had eaten coleslaw, but not all coleslaw eaters (including me!) got ill. A local caterer had prepared the box lunches. Five other groups had also purchased box lunches the same day as our seminar. There were illnesses in two of these groups; those ill tended to also have eaten coleslaw. Investigation is ongoing to determine the source of the contamination of the coleslaw, whether from the foodhandlers who prepared the coleslaw, or from the vegetables (cabbage, carrots, parsley, green onion) which might have been contaminated anywhere along the way from the field to the caterer.

NLVs are spread via the fecal-oral route. They have a propensity for spread during outbreaks because they have a low infectious dose, there may be prolonged asymptomatic shedding, and there is lack of lasting immunity.

2. Unexplained Deaths and Critical Illnesses
In next month's issue of Emerging Infectious Diseases (available now at http://www.cdc.gov/ncidod/EID/vol8no2/01-0165.htm and http://www.cdc.gov/ncidod/EID/vol8no2/01-0150.htm) are two articles describing results of the Emerging Infections Program Unexplained Deaths and Critical Illness of Possible Infectious Etiology project of which we have been a part of since its inception in 1995. We are one of four states that conduct surveillance for these cases. Our case definition for the study was a previously healthy person age 1-49 who had a critical illness or died of what appeared to be an infection, but for which all infectious agent testing had been negative. Laboratory specimens from these cases were banked and at a later time batteries of tests were conducted using syndrome-specific protocols and utilizing molecular-based tests in order to determine the etiology of the illness/death. Infectious causes were identified for 28% of the cases with clinical specimens. All agents identified were previously recognized bacterial and viral pathogens (including Neisseria meningitidis, Chlamydia pneumoniae, and Mycoplasma pneumoniae). No new causative agents were identified. A large proportion of cases remained unexplained, even after extensive laboratory testing. Some illnesses may have noninfectious causes or the testing methods may have been inadequate to detect all agents, particularly viral causes.

The usefulness of this project has extended beyond its original purposes. The surveillance system we set up and the relationship we established with partners such as infection control professionals, intensive care unit managers, medical examiners, and laboratories allowed us to rapidly adapt to surveillance for potential bioterrorism agents. Thank you for your efforts!

3. Lyme Disease
In last week's MMWR was an article detailing Lyme disease in the U.S. (at http://www.cdc.gov/mmwr/preview/
. The number of cases reported in 2000 was at an all time high at 17,730 cases. Minnesota recorded the 10th highest rate of Lyme disease in the country (465 cases). The highest incidence occurred among children aged 5-9 years and adults aged 50-59 years. The highest risk of tick borne disease in Minnesota is not that far off: mid-May through July.

4. Influenza Update
We have had 6 laboratory-confirmed cases of influenza to date. Five have been A/Panama-like (H3N2) the other was B/Sichuan-like; these strains are covered in this year's vaccine. In the last two weeks we have seen an increase of influenza-like illness in schools from southern Minnesota and our first confirmed outbreak in a long-term care facility (in Ramsey County). It's still not too late to get vaccinated and vaccine is readily available statewide.


Bug Bytes is a combined effort of the Infectious Disease Epidemiology, Prevention and Control Division and the Public Health Laboratory Division of MDH. We provide Bug Bytes as a way to say THANK YOU to the infection control professionals, laboratorians, local public health professionals, and health care providers who assist us.

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Updated Friday, November 19, 2010 at 02:16PM