State health officials said they are concerned about a rare strain of virus behind an outbreak of 60 mumps cases in Iowa.
Mary Gilchrist, director of the state’s University Hygienic Laboratory, said the genotype G strain is infrequently seen in the United States. With the number jumping from 17 cases just two weeks ago, she predicted there could be more outbreaks this spring.
“If the past predicts the future, it will get worse in April,” she said.
Recall that, while mumps currently is chucked in there with chickenpox and measles as a “harmless childhood disease,” prior to mass vaccination, mumps, a paramyxovirus, was the leading cause of viral encephalitis in the United States. While not a highly deadly disease, it did account for a large number of hospitalizations and a good deal of morbidity (the fancy name for “bein’ sick”).
And sure enough, it seems to be getting worse. The latest update from the Iowa Dept. of Health Center for Acute Disease Epidemiology notes that as of March 23rd, there have been 187 likely cases of mumps–69 of them confirmed. The age range is all over the scale, but most of them remain clustered in college-age kids (fully a third of the confirmed cases are in students currently attending college). And though the majority of cases have had at least one MMR (measles, mumps & rubella) vaccine, only 65% report 2 doses, with 9% reporting 0. Additionally, I’m not sure how close the vaccine strain is to the G strain causing the outbreak–even with higher vaccination coverage, there may not be enough cross-reaction to get good protection. (Just tiltin’ in the wind a bit here–I couldn’t find much info on the genetics of the vaccine strain or good cross-protection studies involving serotype G–any mumps virologists out there?)
Anyhoo, it will be interesting to compare the molecular epidemiology of the strains (vaccine vs. current outbreak strain). Dr. Gilchrist mentions that the virus may have arrived here on a plane, which may seem a bit strange to folks who are used to thinking of Iowa as more tractors than jets, but recall that many of the cases have so far been here in Johnson county–home to U of Iowa and 30,000 students from not only all over Iowa, but also around the country and the globe. As I’ll discuss further tomorrow, this is fertile ground for an outbreak of infectious disease.