Mumps Update – Indiana and the United States, 2006
Indiana Epidemiology Newsletter
Wayne Staggs, MS
Vaccine-Preventable Disease Epidemiologist
As of August 18, the Indiana State Department of Health (ISDH) has reported 10 cases of mumps in 2006. Two of the cases are classified as confirmed (both by PCR assay) and eight are classified as probable cases. Five of the cases were in children ranging in age from 2-15 years, and five cases were among adults ranging in age from 20-48 years. All cases had symptom onset in the months of March (2 cases), April (4 cases), and May (4 cases).
The ISDH Immunization Program has investigated many reports of suspected mumps cases this year. Since April 24, 2006, oral fluid and/or urine specimens have been collected from 108 persons and analyzed. Two (1.8%) of those 108 persons were confirmed as having mumps by RT-PCR analysis at the Centers for Disease Control (CDC) Laboratory. Outbreaks or significant clustering of confirmed, probable, or suspect cases has not been identified in Indiana. In addition, none of the cases investigated in Indiana had a known direct link to a case from the multi-state outbreak, which began in Iowa and subsequently spread to several other states (see Immunization Works article on page 5).
Several issues and concerns arose during the multi-state outbreak:
The source of the outbreak was not identified, but it may have been connected to a large outbreak that has been occurring in the United Kingdom since 2004. Molecular studies indicate that the Iowa epidemic strain was the same as the one seen in the U.K.
Multiple factors may have contributed to this outbreak and its spread, including: 1) close contact in college and dormitory settings (many of the Iowa cases were college students); 2) lack of two doses of vaccine in college-age individuals and other adults; and 3) delayed recognition, diagnosis, and reporting of cases.
A large proportion of the cases reported having a history (either one or two doses) of immunization against mumps. Since mumps vaccine does not provide protection to all persons and because high coverage levels exist in the United States, it would be expected that most cases would be among vaccinated persons. One dose of mumps vaccine is estimated to have an efficacy of 70-80 percent. Preliminary data from ongoing studies in current and past outbreak areas suggest that two doses of mumps vaccine provides an improved efficacy of 90 percent. It is believed that high coverage levels in exposed populations kept this outbreak from becoming much larger.
Problems interpreting serologic tests for mumps complicated the investigation and epidemiologic analysis of the outbreak in Indiana as well as the outbreak states. Comparison with viral culture and PCR performed at the CDC and the Iowa State Laboratory revealed that serologic (IgM and IgG) testing had poor predictive value for the detection of mumps cases. Therefore, early this summer, the ISDH Laboratory recommended that health care providers collect buccal swabs and/or urine specimens for viral culture and PCR testing, rather than serology. Studies to define the sensitivity and specificity of mumps IgM antibody tests are in progress at the CDC Laboratory. As information becomes available, the ISDH will reevaluate the use of serologic analysis for routine diagnostic testing of mumps disease.
Revised ACIP Guidelines
On June 1, 2006, the Advisory Committee on Immunization Practices (ACIP) published revised recommendations for the control and elimination of mumps. Major emphasis was placed on vaccination of health care workers, school-age children, college students, and international travelers. Those revisions can be found at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5522a4.htm?s_cid=mm5522a4_e
Key revisions to the 1998 ACIP recommendations are as follows:
Acceptable Presumptive Evidence of Immunity
- Documentation of adequate vaccination is now two doses of a live virus vaccine instead of one dose for:
- School-aged children (i.e., grades K-12)
- adults at high risk (i.e., persons who work in health-care facilities, international travelers, and students at post-high school education institutions)
- Routine Vaccination for Health Care Workers
- Persons born during or after 1957 without other evidence of immunity: 2 doses of live mumps vaccine
- Persons born before 1957 without other evidence of immunity: consider recommending 1 dose of live mumps virus vaccine
Indiana Response and Guidelines
As stated above, Indiana received over 100 reports of suspected cases of mumps since the onset of the multi-state outbreak, most of which were ruled out. Each case was investigated, and most had appropriate laboratory specimens collected and analyzed. The ISDH issued revised guidelines for the reporting, clinical diagnosis of mumps, laboratory submission of specimens, prevention through immunization, and other information needed to control mumps disease transmission. These guidelines can be found on the ISDH Web site at http://www.IN.gov/isdh/ (click on Health Professionals and then Disease Information).
During the next few months, the ISDH will issue revised mumps control guidelines and recommendations.
As noted in the August 2006 issue of Immunization Works (published by the CDC National Immunization Program) the multi-state mumps outbreak is subsiding. The entire Immunization Works newsletter can be found at: http://www.cdc.gov/vaccines/news/newsltrs/imwrks/index.html
Immunization Works – August 2006
Mumps Outbreak Subsides: The mumps outbreak that began in Iowa in December 2005 appears to be subsiding, as over 98% of cases had onset dates from January 1 through June 30. From January 1 through July 22, 2006, a total of 4908 cases of mumps were reported to the CDC from 15 outbreak-affected states. The majority of cases, 4894 (98 percent) were reported from eight states (Iowa, Kansas, Illinois, Nebraska, Missouri, South Dakota, Pennsylvania, and Wisconsin) that had endemic, in-state transmission (i.e., outbreak states). An additional 14 cases associated with travel to, or temporary residence in, an outbreak-affected state were reported from seven states (Colorado, Minnesota, Mississippi, New York, New Mexico, Michigan, and Texas). It is expected that once the outbreak is over, the number of cases being reported each week will be higher than in previous years, due to improved mumps surveillance.
The age-group-specific incidence was highest among persons 18-24 years old (32 per 100,000), reflecting transmission in college and university settings. While most cases occurred among persons who had received two doses of mumps-containing vaccine (the vaccine has an estimated efficacy of 90 percent), preliminary data suggest attack rates were higher among persons who had received only one dose of vaccine. In July, the American College Health Association (ACHA) distributed a letter to universities and colleges across the United States. The letter encouraged the vaccination of enrolled students with two doses of MMR vaccine before returning to school. State and local health departments are encouraged to remain vigilant for mumps cases, especially among college and university students when they return to school in the fall. For more information about mumps, please visit the CDC’s mumps website at: https://www.cdc.gov/mumps/.