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Mumps Is Back

A high vaccination rate did not prevent a large outbreak of mumps in Iowa.

After the introduction of live attenuated mumps vaccine in 1967 and its incorporation into the mumps-measles-rubella vaccine a decade later, mumps became rare in the U.S. Iowa averaged five cases annually from 1996 through 2005. In 2006, however, 219 cases were reported to the Iowa Department of Public Health by March 28.

The median age of patients was 21 years (range, 3–85 years); 48% of patients were 17–25 years old, and 30% were college students. Of the 133 patients with known vaccination histories, 65% had received the recommended two doses of vaccine, and 14% had received one dose. The most common symptoms were parotitis (83%), submaxillary/sublingual gland swelling (40%), fever (36%), and sore throat (32%). Complications (e.g., orchitis) occurred in 5% of patients. Average duration of illness was 5.1 days. The mumps virus isolated in an unspecified number of cases was genotype G, but only 16% of the 219 cases could be linked epidemiologically, indicating multiple subclinical source cases.

Comment: Mumps vaccine is among the most effective childhood vaccines. Routine immunization has reduced the incidence of mumps in the U.S. by 99%, presumably through production of herd immunity. However, introduction of the virus, perhaps from a U.K. outbreak in 2005, has caused a major outbreak in people assumed to be protected; >800 confirmed or suspected cases have now been reported in Iowa. A separate CDC report pinpoints air travel as a potential disseminator of this infection and raises the issue of transmission of other respiratory pathogens for which we have less vaccine-induced immunity.

— Stephen G. Baum, MD

Published in Journal Watch Infectious Diseases April 21, 2006

Citation(s):

Centers for Disease Control and Prevention (CDC). Mumps epidemic — Iowa, 2006. MMWR Morb Mortal Wkly Rep 2006 Apr 7; 55:366-8.

• Medline abstract (Free)

Centers for Disease Control and Prevention (CDC). Exposure to mumps during air travel — United States, April 2006. MMWR Morb Mortal Wkly Rep 2006 Apr 14; 55:401-2.

• Medline abstract (Free)