1. Mumps Outbreak on a University Campus Kansas, 2006
Angela Song-En Huang, MD MPH
Kansas Department of Health and Environment
State Branch/CDD/OWCD
Good morning

2. Mumps Only known cause of epidemic parotitis
A vaccine preventable disease
1967- Live-attenuated mumps vaccine licensed
1977- One dose of measles-mumps-rubella vaccine (MMR) recommended
1989- Two doses of MMR recommended
Now a rare disease
Mumps is the only known cause of epidemic parotitis and is a vaccine preventable disease. The live attenuated mumps vaccine used in the United States was first licensed in 1967, and later became part of the measles-mumps-rubella vaccine. In 1977, the Advisory Committee on Immunization Practices recommended a single dose of MMR for children aged 12 months or older. (PAUSE) In 1989 they revised their recommendation to include a second dose of MMR in response to a large outbreak. Routine use of the vaccine has made mumps a rare disease throughout the United States and outbreaks even less common.

3. Mumps Outbreak at the University of Kansas (KU) — 2006
March 24 - First case in a KU student
March 27 - Two more cases from KU
April - Clusters of cases reported in universities around the state KU
157 Cases
However, an outbreak occurred at the University of Kansas in (PAUSE) On March 24, the first case of mumps at KU was reported to the state health department. Three days later two more cases were reported at KU. All three cases lived in the same sorority house. Over the next month, other universities around the state reported cases but KU was the only school which had a large outbreak with 157 cases reported by the end of April.
Fort Hays State Univ
4 Cases
Kansas State Univ
2 Cases

4. Objectives Institute control measures
Describe the outbreak at the University of Kansas (KU)
Identify risk factors for disease
Assess mumps vaccine coverage
An investigation was launched to (PAUSE): institute control measures; describe the outbreak at KU; identify risk factors for developing disease; and assess mumps vaccine coverage.

5. Control Measures Isolation of cases Up to April 6: 9 days
After April 25: 9 days
Information disseminated to students
After the cluster of cases was identified at KU, the state health department sent out a notice to physicians and public health practitioners through the secure, web-based communication system of the Kansas health alert network.
The first notice recommended a 9 day isolation period. On April 7th, isolation was changed to 4 days, because the infectious period of mumps was considered to be up to 4 days after onset of active disease, and it was thought that this would increase compliance with isolation orders.
However, the isolation period was changed back to 9 days on April 25, after definitive guidelines were published by CDC and to comply with Kansas regulations.
KU’s student health service disseminated information from the state and local health department to the students using posters, and the school newspaper.

6. Outbreak Description Method Case finding using surveillance data
Review medical records
Case definition:
KU student with disease onset February 1–May 8, 2006
Had one of the following:
Acute onset of parotid or other salivary gland swelling or pain without other apparent cause
Isolation of mumps virus
PCR positive for mumps
Physician diagnosis of mumps
Databases from the state health department, the local health department, and the student health service were used to identify mumps cases. We then reviewed medical records to ascertain cases. A case was defined as illness in a KU student with disease onset between February 1 and May 8, 2006, who had one of the following:
Acute onset of parotid or other salivary gland swelling or pain without other apparent cause, isolation of mumps virus from a clinical specimen, identification of mumps virus using polymerase chain reaction or PCR, or physician diagnosis of mumps.

7. Mumps at KU — February 1–May 8, 2006 (n=174)
Isolation Days 9 4 9
Last week of classes
First case reported
This is the epidemic curve of the outbreak. A total of 174 cases were reported. Even though the first case of mumps was reported to the state health department on March 24, several cases had onset dates earlier than that.
The number of cases rose throughout April, peaking in the third week. This was followed by a sharp fall in the week starting May 3. Interviews with physicians at the student health service found that, after isolation days were changed back to 9 days on April 25th, physicians were more selective in making the diagnosis of mumps//because of the perceived social and educational impact on the students.

8. Mumps at KU — February 1–May 8, 2006 (n=174)
Characteristics
Mean age, years
20.9 (range )
Sex
Male
35%
Female
65%
Lived in dorms
28%
Student Level, n
Graduate
10 (Attack Rate=0.2%)
Undergraduate
164 (Attack Rate=0.8%)
The mean age of the cases was 20.9 years.
35% were male; 65% were female.
28% of the students with mumps lived in the dorms.
10 cases were found in graduate students, and 164 in undergraduate students. The attack rate was lower in graduate than undergraduate students.

9. Methods for Case-Control Study
Cases
Responded to telephone interview AND met a stricter case definition
Controls
Telephone survey of randomly selected sample of undergraduate students
c2-test and t-test to compare cases and controls
Calculate odds ratio
Review vaccination records
To identify risk factors associated with disease, we conducted a case-control study among the undergraduate students.
Cases were interviewed by telephone and then selected based on a stricter definition than was used for initial case finding.

10. Case Definition for Case-Control Study
Answered “yes” to:
“Did you have swelling of the parotid glands, the glands near your ears/cheeks?” and lasted ≥2 days OR
“Did you have swelling or pain in your testicles?”
Culture or PCR positive for mumps virus
A case was defined as anyone who answered “yes” to the question “Did you have swelling of the parotid glands, the glands near your ears/cheeks?” and lasted 2 or more days, or males answering “yes” to the question “Did you have swelling or pain in your testicles?”
In addition, anyone with culture or PCR positive for mumps virus was included.

11. Methods for Case-Control Study
Cases
Responded to telephone interview AND met a stricter case definition
Controls
Telephone survey of randomly selected sample of undergraduate students
c2-test and t-test to compare cases and controls
Calculate odds ratio
To select controls, we conducted a telephone survey of 444 randomly selected undergraduate students.

12. Methods for Case-Control Study
Cases
Responded to telephone interview AND met a stricter case definition
Controls
Telephone survey of randomly selected sample of undergraduate students
c2-test and t-test to compare cases and controls
Calculate odds ratio
We compared the cases and controls using chi-square test and t-test and calculated the odds ratio.

13. Selection of Cases and Controls
10 graduate students
1 student with disease
164 cases
443 controls
From the 174 cases identified, 164 were eligible for the study after 10 graduate students were excluded. Of these, 126 (or 77%) responded to our telephone survey. 97, or 77% met the stricter case definition.
From the 444 randomly selected controls, one student was excluded because he had disease. Of the remaining 443, 147, or 33% responded to the telephone survey.
126 (77%) responded to survey
147 (33%) responded to survey
97 (77%) met case definition

14. Statistically Significant Risk Factors
Cases
n=97
Controls
n=147
OR (95% C.I.)
Exposure to persons with mumps
34%
16%
2.8 (1.4, 5.5)
Female
62%
44%
2.0 (1.2, 3.6)
Lived in dorm
26%
14%
2.1 (1.0, 4.2)
Worked on campus
25%
2.0 (1.0, 4.0)
Analysis of the case control study revealed that several risk factors were significantly associated with illness.
We asked the students “during the month before your illness, were you in close contact (meaning within three feet for several hours) with someone who was ill with mumps?” The odds of having answered “yes” to this question among cases was 2.8 times as high as the odds of answering “yes” among the controls. Other statistically significant risk factors were being female, having lived in the dormitory, or having worked or volunteered on campus.

15. Statistically Significant Risk Factors
Cases
n=97
Controls
n=147
OR (95% C.I.)
Age (years)
18-19
41%
18%
6.0 (2.9, 12.7) 20
23%
24%
2.6 (2.9, 12.7) 21
21%
16%
3.4 (1.5, 7.7)
≥22
15%
Reference
The odds of being younger than 22 years of age were up to six times greater among cases compared to controls.
Other risk factors including sharing spaces, working, or participating in sports or travel were not found to be significant.

16. Vaccine Coverage Cases (n=97) Controls (n=147) p-value
Obtained complete record
99%
95%
0.09
≥2 doses of MMR
(All subjects)
98%
0.24
Finally, we reviewed immunization records of the students to assess vaccine coverage.
We were able to obtain immunization records for 99% of the cases and 95% of the controls. The proportion of students with 2 or more doses of MMR were similar.

17. Conclusion Outbreaks occurred in vaccinated population
Vaccination can limit the extent of outbreak
Outbreak control relied on early diagnosis and isolation of cases
Early cases were not promptly diagnosed and reported
Changing isolation days created confusion
Cases had increased odds of known exposure to mumps cases, female, younger age, or living in dorms
This investigation showed that an outbreak of mumps occurred in a highly vaccinated population. 99% of the students at KU had at least 2 doses of MMR. The attack rate observed in this investigation was 0.8%, which is much lower than the 30% observed in the pre-vaccine era. This shows that vaccination can limit the extent of mumps outbreaks. With a high vaccination rate among KU students, outbreak control relied on early diagnosis and isolation of cases. However, because mumps is now a rare disease, early cases were not promptly diagnosed and reported. Additionally, changing the recommended number of isolation days during the outbreak created confusion among both clinicians and public health practitioners.
From the case-control study, it was shown that cases had increased odds of having known exposure to mumps, being female, being in the younger age group, or living in dormitories. Similar risk factors were also identified in a outbreak among university students in the Midwest.

18. Limitations Low response rate among controls Recall bias
Case definition relied on self-reporting of parotid enlargement
Lacked accurate laboratory test for diagnosis
There are limitations to this investigation. The response rate was low among controls. However, the controls interviewed were representative of all controls selected. Recall bias was a concern in this investigation because cases could have been more likely to remember exposures than controls. In addition, controls were interviewed later than cases. Our case definition relied on self-reporting of parotid enlargement which was difficult to describe over the telephone. However, parotid enlargement should have been easily recognized by patients. Lastly, because there were no reliable laboratory diagnostic tools to confirm all cases of mumps, capturing true cases relied on having a strict clinical case definition.

19. Recommendations
Mumps should be considered in patients presenting with parotitis
Congregate living settings may facilitate disease transmission
Continue efforts to maintain high vaccine coverage
This investigation suggests that physicians should consider mumps as a differential diagnosis when patients present with parotitis, regardless of the patient's vaccination status. Public health investigators should encourage compliance to control measure during an outbreak especially for congregate living settings, such as dormitories, which may facilitate disease transmission during a mumps outbreak. Finally, we must encourage continued efforts to maintain high vaccine coverage to limit outbreaks.

20. Acknowledgements Lawrence County Health Department Barbara Schnitker
DeeAnne Schoefeld
Linda Cowles
Kathy Colson
Kim Ens
Watkins Memorial Health Center
Patricia Denning
Patty Quinlan
Sherry Rhine
Diane Hendy
KDHE
Gail Hansen
D. Charles Hunt
Jennifer Hill
Martha Siemsen
Daniel Neises
Trudy Shane
CDC
Margaret Cortese
Aaron Curns
Rebecca Bitsko
Hannah Jordan
Fatma Soud
Jose M. Villalon
Gustavo Dayan
Kate Wytovich
Charles LeBaron
Mona Marin
Susan Reef
Mumps Response Team
Diana Bensyl
I would like to acknowledge the many people who worked on this outbreak.
Thank you.
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention