Public Health Investigation and Response to a Varicella Outbreak in Uinta County, Wyoming 37th National Immunization Conference March 17-20, 2003 Chicago, Illinois Presented by: Christy Remick Surveillance Coordinator Wyoming Department of Health Cheyenne, Wyoming

Introduction

Wyoming Department of Health Reportable Diseases and Conditions list May 2001: Chickenpox January 2003: Varicella (chickenpox or shingles) Unusual illnesses or clusters of illnesses Chickenpox was a reportable disease beginning in May 2001 in the state of Wyoming. We just recently changed our Reportable Diseases and Conditions list to include both chickenpox and shingles. The inclusion of shingles was not only due to this outbreak, but also because of the thought that shingles disease may increase due to the varicella vaccine. Unusual illnesses and clusters of illnesses have been reportable prior and could include chickenpox outbreaks… although many individuals in Wyoming do not feel varicella is out of the ordinary.

Public Health Nursing (PHN) Uinta County Public Health Nursing (PHN) Services Physician report to Uinta County PHN manager UC PHN local follow-up PHN report to WDH A newer Uinta County physician called his local Public Health Nursing office to see if other physicians in the area had been seeing an increase in chickenpox cases. The Uinta County Public Health Nursing manager called the other physician office and also the local OB-GYN clinic. It was found that their was an increase in chickenpox cases in the area… with the OB-GYN clinic seeing three pregnant women who had been exposed to the disease. Of the three pregnant women… only one was adequately protected against the disease. The other two pregnant women were given immune globulin because their titers showed they had no immunity. On June 18, 2002, the Uinta County Public Health Nursing manager called the Wyoming Department of Health to report their findings.

PHN and WDH collaborations Reasons for investigation High-risk populations Pregnant women involved Minority group (location) Adults involved Bioterrorism Grant PHN volunteers to take the lead Conducts interviews Provides educational information The Wyoming Department of Health made the decision to investigate the suspected chickenpox outbreak for several reasons: Not only were there pregnant women involved, in which varicella can be life-threatening to both the fetus and expectant mother, but it was also originally reported that there was a high percentage of varicella in the Hispanic population. Another reason the decision was made to investigate was because of the high proportion of adults involved. A year prior to this outbreak, the Wyoming Department of Health investigated another suspected varicella outbreak in an adult population that turned out not to be chickenpox. A final reason for investigation was due to the Bioterrorism Grant agreement that states all rash-like illnesses are to be investigated. The UC-PHN manager volunteered to take the lead in the investigation because she had new nurses on staff that could benefit from the investigation experience. The UC-PHN office conducted interviews with the patients from the physician offices. In doing so, they received additional contact names. An educational piece was added into the phone interviews.

Second Wave Uinta County Community Event Fishing Derby 235 children in attendance adult volunteers and parents Immediate Public Health Action Public Awareness regarding varicella Confirmation of varicella The UC-PHN office called on July 1st to report a new suspect case of chickenpox in a 38 year old male who attended a community event. It was reported that this man possibly exposed several children during his most infectious period while tying fishing line for the kids at a Fishing Derby. There were 235 children who attended this community event and 133 adults. Because of the high numbers of children involved, immediate PH action took place. UC-PHN and WDH decided to inform the public of the current varicella outbreak through a press release detailing the outbreak, recommendations, vaccine information, possible exposure at the Fishing Derby, and public health contact information. UC-PHN again volunteered to lead the investigation and contacted all participants via telephone. All participants were offered the varicella vaccine due to lab results confirming varicella.

Materials and Methods

Investigation Questionnaire Line Listing Disease verification Contact information Table to list: participants, age, previous varicella, vaccination history / date, referral for vaccine Section to list non-registered participants Line Listing Disease verification Specimen collection method Laboratories The Centers for Disease Control and Prevention North Dakota Public Health Laboratory Questionnaires were filled out for all suspected varicella cases. The questionnaire consisted of three sections: 1) participant contact information (address, telephone number), 2) a table to list all of the individuals that attended the event, whether a child or adult, age, previous disease (chickenpox), the date of vaccination if previously vaccinated, and whether referred for vaccination or booster, and 3) a section to list the names and phone numbers of others that attended the event, but had not registered. A line listing was made for everyone who filled in a questionnaire. The Wyoming Department of Health – Disease Intervention Specialist in the named area, along with the UC-PHN office staff performed serum collection and swab/slide collection for varicella testing. Serum samples were sent to the Wyoming Department of Health’s contract laboratory – the North Dakota Public Health Laboratory, while the swabs and slides were sent to the VZV laboratory at the CDC.

Analysis Graph by month of illness Graph by onset of illness date Epi Plot by onset of illness Analyses of the line listing data included: A graph by the month of onset, A graph by the onset of illness date, and also An epi plot by the onset of illness date.

Vaccination Determining susceptibility Vaccine supply (WDH) PHN questionnaire Vaccine supply (WDH) 160 doses of vaccine ordered adults offered vaccine free-of-charge Vaccine administration (PHN) vaccination clinic answering service Susceptibility was determined through a questionnaire developed by UC-PHN. The Wyoming Department of Health – Immunization Program ordered 160 doses of the varicella vaccine to be delivered directly to the UC-PHN office. The Wyoming Department of Health supplied the vaccine doses needed for adults 19 years of age and older, while children 18 years and younger received their vaccination through the Vaccine for Children program. The UC-PHN office administered the varicella vaccine to the public during an arranged vaccination clinic. The UC-PHN office also provided answering services for concerned patrons.

Education Press release Epi X posting Presentation Wyoming Public Health Association Conference 37th National Immunization Conference Along with public education through telephone interviews, the population at large was informed about varicella and the current outbreak in their community through a press release. Public Health officials were also notified of Uinta County’s varicella outbreak via an epi X posting detailing the outbreak. The UC-PHN manager and myself also presented a brief presentation regarding this varicella outbreak at the Wyoming Public Health Association Conference.

Results

Questionnaire Varicella Shingles Male 13 2 Female 8 5 Age range   Varicella Shingles Male 13 2 Female 8 5 Age range 7 mos. - 38 yrs 11 - 82 yrs Median age 9.5 yrs 46 yrs Previous varicella: Yes 1 6 No 17 Don't Know 3 Vaccination: 7 Rash range * 3 - 10 days ** 7 - 21 days Average days for rash * 7 days ** 14 days * Out of 17 cases because 4 cases still had rash present. ** Out of 4 cases because 3 cases still had rash present. This shows a few things that were collected on the modified varicella questionnaire.

Laboratory Confirmed Epi-link Confirmed Probable Not a case Varicella   Confirmed Epi-link Confirmed Probable Not a case Varicella 6 3 9 Shingles 7 N/A Total 13 Four serum samples came back VZV wild-type virus positive from the ND PHL. In discussion with CDC during this time (due to the large community event)… it was stated that serum testing for varicella is very time sensitive. CDC requested swabs and slides for the two cases that recently came back negative from ND PHL. Although public health action was immediately enacted after the possible community event exposure… test results from CDC verified the individual was positive for VZV wild-type virus. Another confirmed case was also reported. In addition, 3 cases were epi-linked positive and there were 3 probable cases. 9 reported cases could not be considered confirmed nor probable according to CDC’s clinical case definitions. The CDC also stated via a telephone conversation that a confirmed shingles case could be defined as a physician diagnosis of shingles. All seven reported shingles cases were doctor diagnosed.

Graph This graph shows the varicella outbreak by month of diagnosis. 43% of the cases occurred in June, which is slightly abnormal for a varicella outbreak.

Epi Plot An epi plot was made to show the outbreak by onset of illness date and to determine case associations. As an example, in the brother-sister relationship… the brother was most likely the source for the sister’s infection based on the incubation period for the virus.

Vaccination 111 children had disease history   Total Susceptible Vaccinated Pregnant Previous Vaccine Children 235 42 21 82 Adults 133 13 8 3 1 111 children had disease history All 3 pregnant women had disease history OB-GYN referral was made In addition, 4 infants attended All 4 mothers reported disease history This graph shows the data collected during the telephone questionnaire following the community event. Follow-up: Of the 42 susceptible children, 23 were reached for further follow-up….. 7 of these children learned they did have prior disease and 16 remain disease free five weeks after possible exposure. Of the 13 susceptible adults, 9 were reached for further follow-up….. 1 learned he had the disease as a child and the remaining 8 were disease free after 5 weeks.

Discussion

WDH Lessons Learned Importance of timely reporting Verification of outbreak Obtaining control Prevention measures Effects of in-depth surveillance and prevention Public awareness effect on possible large exposure PHN vaccination clinic and local coordination prevention of further disease The investigation of this outbreak revealed several important messages to WDH: First, it showed the importance of timely reporting. If this outbreak were not reported in the early stages, not only would specimen collection have been nearly impossible, but the community event exposure may have went unnoticed and unreported. One critical component of this outbreak was the collaboration between the local public health nursing office and the state department of health. Without this collaboration, coordination of the outbreak would have never been obtained. If neither collaboration nor coordination took place… prevention of further disease would have been impossible too.

WDH Lessons Learned Importance of proper education for physicians Serology timing, best test for varicella Serum: range between 7 – 14 days Swab: during the vesicular stage Why outbreaks should be investigated Verification of disease Collaboration skills Outbreak investigation practice Another lesson learned is the importance of proper education for physicians on the need for confirming diseases through laboratory tests. Most physicians rely on clinical diagnoses; however in outbreak situations, it is necessary to confirm the disease from a public health standpoint. Since confirmation of the disease is critical in an outbreak setting… a critical lesson learned involved the serology timing for varicella testing. If the individual is within 7 – 14 days of the rash illness, then serum collection would be most appropriate, however if the individual is in the vesicular stage of the disease then a swab specimen of the lesions would supercede. Three major reasons why outbreaks should be investigated… no matter how minor of a disease the community may believe… include: Verifying the disease at hand, Brushing up on collaborative skills, and Utilizing every possible chance for practicing investigation skills… especially in a BT era.

Thank You!