Norovirus in Vermont outbreak detection

Norovirus in Vermont outbreak detection. On the morning of February 5, the mother of a young child called the Vermont Department of Health (VDH) to report a possible foodborne outbreak. The woman’s child, age 5 years, and two neighborhood children, ages 7 and 10 years, had become ill with vomiting and diarrhea within 12 hours of each other.

The child aged 5-years had become so sick that her mother had taken her to the emergency department at the local hospital.

The mother reported that her child initially complained of nausea around 10:00 a.m. on Monday, February 2. The nausea was followed by vomiting and multiple episodes of diarrhea. The child was unable to eat or drink anything without vomiting. Toward evening, the child became listless. The woman took the child to the emergency department where she was noted to be dehydrated and that she had a fever. Stool and blood specimens were collected, and the child was treated with intravenous fluids and released.

The mother called the emergency department the following day to receive the test results for her child. A nurse told her that preliminary stool culture results were “negative for the usual bacteria.”

The two neighborhood children had had similar symptoms (i.e., nausea, vomiting, diarrhea, and fever) but had not become as ill as the woman’s child. Their symptoms started a few hours earlier than her child’s. Both had returned to school the day after becoming ill.

The three children usually did not play together but had attended a birthday party on the morning of Sunday, February 1. The mother was concerned about homemade ice cream that was served at the party because she had heard it had been prepared using raw eggs.

After confirming the mother’s information with the emergency department physician, VDH staff called the mother who had organized the February 1 birthday party. The woman reported that her own child was well (except for a cold). Other parents had called her, however, saying that their children had become ill with vomiting and diarrhea.

The woman reported that her son’s birthday party had occurred at a private indoor swim club in Essex, Vermont, close to Burlington. Approximately 30 children and adults were in attendance. The children ranged in age from 5 to 10 years. Not all of the children attended the same school.

Cake, ice cream, and canned drinks had been served at the party. All refreshments had been commercially prepared. The ice cream had not contained raw eggs.

The majority of children had played in the pool at the swim club before presents were opened and cake and ice cream were served. Two children who later became ill had left the party before cake and ice cream were served to attend another birthday party.

The mother provided a list of party attendees, indicating which ones she knew had been ill, and their telephone numbers. She also provided the name and telephone number for the swim club manager.

PART II. HYPOTHESIS GENERATION 

VDH investigators notified the district health department of the problem and then contacted the manager of the private swim club. The manager stated that he was dealing with a “problem” and refused to talk with health department investigators. He suggested that they leave their telephone number and he would call them back if he had time.

After VDH investigators stated the reason for their call and reassured the swim club manager that the health department needed to investigate the reported illnesses so that the source could be found and actions could be taken to prevent others from becoming ill, the manager spoke with investigators.

The manager had not heard about the illnesses associated with the February 1 birthday party, but had received reports of illness among other persons who had used the pool during the weekend. Rumors were circulating that participants in the infant-mother swim class (that last met on Saturday, January 31) were sick with “stomach flu.”

The manager provided VDH investigators with the names and contact information for persons who had complained to him about being ill and for members of the infant-mother swim class.

VDH investigators, with the assistance of district health department staff, contacted households of persons who had visited the swim club and reported illness since January 27 to VDH, the mother organizing the February 1 birthday party, or the swim club manager. Investigators asked about specific symptoms, the date of illness onset, and the most recent date the ill person had visited the swim club.

On the basis of these calls, 21 persons were identified as having attended the swim club and having reported being ill (Table 1). Signs and symptoms included vomiting (90%), nausea (81%), abdominal cramps (67%), diarrhea (48%), fever (48%), and headache (43%). Symptoms began a median of 30 hours (range: 8−62 hours) after visiting the swim club.