Minnesota Department of Health (MDH) Bug Bytes
August 12, 2004
Vol. 5: No. 7
Topics in this Issue:
1. E. coli O157:H7 Outbreak #1
2. E. coli O157:H7 Outbreak #2
3. First West Nile Cases
4. Pertussis Increasing
5. TB Grand Rounds
6. Emerging Infections Conference
7. Welcome to Our New EIS Officer
Last week, we announced an E. coli O157:H7 outbreak to warn consumers of a contaminated product. Through our robust active laboratory-based disease surveillance system that includes mandatory isolate submission, real time isolate confirmation and molecular subtyping, and timely interviewing of case-patients, we likely prevented additional cases. We have had four Minnesota cases reported, all with isolates of the same pulsed-field gel electrophoresis (PFGE) subtype. A case-control study demonstrated an association with consumption of Northern Plains frozen ground sirloin patties purchased at Sam's Club stores; an additional case occurred in a Wisconsin resident who had purchased the same product at a Sam's Club in Waukesha.
Onsets of illness ranged from July 10 to July 24. One case-patient was hospitalized, and all have recovered.
The Minnesota Department of Agriculture (MDA) traced the ground sirloin back to a meatpacker in Columbus, Nebraska. Due to our press release, the U.S. Department of Agriculture Food Safety and Inspection Service initiated a voluntary recall of approximately 500,000 lbs. of the product. MDA has isolated E. coli O157:H7 from opened and unopened packages of the patties retrieved from patient's homes and individual stores; PFGE results are pending.
Two astute clinicians clued us to early recognition of a second E. coli O157:H7 outbreak late last week. They both called regarding individual E. coli O157:H7 patients, alerting us to the cases and the fact that both of their patients had become ill while riding on the MSTram, a 300 mile bicycle ride across central Minnesota that took place July 25 to July 30 to raise funds for the National Multiple Sclerosis Society, Minnesota Chapter. Nearly 1,000 riders from 24 states and two Canadian provinces participated, the majority being from Minnesota. We obtained an email list from the ride organizers and alerted all the riders of the situation. We have interviewed several hundred riders.
To date, we have had five confirmed cases. PFGE subtyping has been completed on three cases to date and all matched (different subtype from outbreak #1). In addition, we have found nine persons who are suspect cases in that they had diarrhea of at least 2 days duration with cramping. Illness onsets ranged from July 27 to 31. The age range of cases is 22 to 72 years (median, 52). At least one individual was hospitalized. Our investigation revealed an association of illness with a spaghetti dinner (spaghetti sauce with meat) served by a church on July 26 to 260 riders. An investigation into food preparation and source of the ground beef for that meal is ongoing, but it does not appear that the general public is at risk from commercially available contaminated ground beef. We are happy to note that despite their illness most of the ill riders were able to complete their ride (that's true dedication!).
In the last week, we have had three human cases of West Nile virus (WNV) reported in Minnesota including a 28 year-old male from McLeod County with onset of fatigue, headache, and fever on July 12; a 59 year-old male from Wright County with onset of fever and headache on July 21; and a 40 year-old male from Lyon County with onset of meningitis on July 16. The 40 year-old was hospitalized. Serum was positive for WNV IgM antibody at both clinical laboratories and at MDH.
In Minnesota, we also have had 94 WNV-positive birds from 27 counties. To date, there have been three equine cases, from Goodhue, Wright, and Benton Counties. No mosquito pools have tested positive yet. As in past years, we still expect the greatest risk to humans to be from mid-July through mid-September with a peak in mid to late August.
Reported pertussis cases have increased in recent weeks in Minnesota and nationally. We have seen 145 cases as of July 31, compared with 79 cases as of this date in 2003. Wisconsin has reported over 1,000 cases to date in 2004, occurring primarily in the southeastern region of the state. North Dakota has reported an outbreak of over 140 cases in the north central region of the state.
The recent increase is not necessarily unexpected, given that pertussis normally peaks every 3 to 5 years, and the most recent peak incidence year was 2000. We will likely see continued increases in cases, as pertussis tends to peak in late summer and fall. Furthermore, pertussis remains endemic and is considered to be under-diagnosed and under-reported particularly among adolescents and adults; therefore, provider notifications and media reports tend to increase reported cases due to greater awareness and a higher index of suspicion for pertussis in the differential diagnosis of cough illness.
Providers are encouraged to consider and test for pertussis for:
- Individuals exhibiting a prolonged cough, especially a cough lasting greater than 2 weeks,
- Individuals exhibiting a paroxysmal cough, especially with post-tussive vomiting or whoop,
- Individuals exhibiting a cough illness and who have had a known exposure to an infectious case of pertussis within 3 weeks prior to cough onset, and
- Infants and other individuals with symptoms consistent with pertussis and who are critically ill or at high risk of serious complications of pertussis.
Suspect cases of Bordetella pertussis infection can be confirmed by culture or polymerase chain reaction (PCR). Whenever possible, both PCR testing and culture should be performed. Serology is not currently standardized and is also not currently considered reliable for laboratory confirmation.
While the incidence of tuberculosis (TB) is decreasing nationally, this is not the case in Minnesota. Because of the complex nature of many of Minnesota's TB cases, diagnosing, treating and controlling the TB transmission present significant challenges for medical and public health professionals. Most (80%) TB cases in Minnesota occur among persons born outside of the United States, presenting significant cultural and language barriers. In addition, the incidence of drug resistant TB and extrapulmonary TB are higher here than the national average.
To bring together medical and public health professionals to discuss challenging clinical and public health aspects of selected TB cases, TB clinical case conferences are held the first Wednesday of each month at the MDH Snelling Office Park facility in St. Paul. The case conferences are free of charge and all interested clinicians and public health professionals are encouraged to attend. Continuing medical and nursing education credits are offered. Case conferences are co-sponsored by the Minnesota Institute of Public Health, St. Paul Ramsey County Department of Public Health, The American Lung Association of Minnesota, and MDH.
See: TB Clinical Case Conferences for a map/driving directions and more information.
We are pleased to announce that once again we will be co-sponsoring the 10th Emerging Infections in Clinical Practice and Emerging Health Threats Conference. The conference will be held Friday, November 12 in Minneapolis. Topics and speakers include Robert Weinstein from Cook County Hospital speaking on antibiotic resistance and healthcare associated infections, and Robert Webster from St. Jude Children's Research Hospital speaking on pandemic influenza. Other topics include a pneumonia update, new developments in antibiotics, travel medicine, hepatitis viruses, infectious agents and the blood supply, and a national terrorism and preparedness update. Brochures will be mailed shortly and you may receive more information by calling the University of Minnesota Continuing Medical Education at (612) 626-7600 or view at http://www.med.umn.edu/cme/.
We are pleased that our new Epidemic Intelligence Service officer from the U.S. Centers for Disease Control and Prevention has arrived to start his 2-year training with us. His name is Steve Swanson. He has an undergraduate degree from the University of Minnesota, a medical degree from Harvard University, and is board certified in pediatrics. He has trained in pediatric infectious diseases at Children's Hospital and Research Center at Oakland and Washington University. He also has extensive medical experience and training in Africa. We already have him busy on an investigation!
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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