Norovirus in Vermont

These Epidemiologic Case Studies are based on historical events and include epidemiologic methods that were practiced at the time. Given the historical nature of this content, the methods that are referenced on this site may be outdated practices in some settings. As some of the practices are still used, they continue to offer educational value.

Target Audience

This case study was developed for students and public health professionals interested in learning and practicing specific skills in outbreak investigation, especially outbreaks associated with recreational waters. The target audience includes epidemiologists, environmental health specialists, sanitarians, public health nurses, disease investigators, health officers, and physicians.

Learning Objectives

After completing this case study, the student should be able to

  • List categories and examples of questions that should be asked of key informants who report a suspected infectious disease outbreak
  • Discuss considerations in working with businesses that might be identified as a possible source of an outbreak
  • Outline components of swimming pool design and operation that help prevent the transmission of pathogenic agents
  • Discuss the action of chlorine to disinfect water and factors that influence its effectiveness
  • Interpret test results for chlorine and pH with respect to swimming pool water quality
  • Identify activities that increase a person’s risk for exposure to pathogens in recreational water
  • Interpret results from a cohort study, including attack rates, relative risks, and P values
  • Describe the steps for management of fecal incidents in treated recreational water venues


Successful completion of basic training in infectious disease epidemiology, descriptive epidemiology, study design, measures of association, and outbreak investigation. The student also will benefit from having familiarity with water treatment processes at swimming pool venues and evaluation of these systems but probably will rely on others with greater expertise in these areas during a real-life outbreak.






2.5 – 3 hours.

Continuing Education

Continuing education credits are not available for completing this case study.

Developed By

Jeanette K. Stehr-Green, MD, developed this case study in collaboration with individuals from the Centers for Disease Control and Prevention:

  • National Center for Zoonotic, Vector-borne, and Enteric Diseases
  • National Center for Environmental Health
  • National Center for Immunization and Respiratory Diseases

Original Investigation Team

The following individuals investigated the original outbreak of norovirus in Vermont: L. J. Podewils, MS, PhD; L. Zanardi Blevins, MD, MPH; M. Hagenbuch, D. Itani, MS; A. Burns; C. Otto; L. Blanton, MPH; S. Adams; S. S. Monroe, PhD; M.J. Beach, PhD; and M. Widdowson, VetMB, MSc.