You may actually see cases of mumps in the coming year. It's time to get reacquainted with what it looks like, what the complications are, and what the control measures are.
As of the first week of May, a mumps outbreak that began in December 2005 with a few reported cases at a university in eastern Iowa had grown to more than 1,500 confirmed, probable, and suspected cases in Iowa, along with several hundred additional cases reported in Illinois, Indiana, Kansas, Michigan, Minnesota, Missouri, Nebraska, and Wisconsin.
Compare that with an average of just 5 mumps cases per year in Iowa since 1996 and 265 cases annually for the entire country since 2001, and it's obvious we've got a problem that could stay with us for a while.
Mumps is an acute viral illness, first described by Hippocrates in the 5th century. Approximately 40%–50% of patients present with unilateral or bilateral parotitis and fever, while another 20%–30% are asymptomatic.
Before the measles-mumps-rubella (MMR) vaccine entered the U.S. market in 1967, a physician who saw a child with parotitis would automatically think of mumps.
Today, we're more likely to suspect that submaxillary/sublingual swelling is related to lymphadenitis, and a sore throat with fever to strep throat.
Some patients complain of pain in the corner of the jaw and/or an earache, which can be confused with otitis.
For the time being at least, we need to resurrect our clinical suspicion for mumps in order to avoid giving unnecessary antibiotics.
Once you suspect mumps, you can culture the nasopharynx, throat, or urine or do a serology looking for IgM antibodies. Check with your laboratory to make sure that the viral culture they perform will identify mumps because standard shell vial culture could miss it.
Although usually self-limited, mumps can cause complications such as meningitis, encephalitis, inflammation of the testes or ovaries, myocarditis, arthritis, and deafness.
Any of these can occur in the absence of parotitis.
Symptomatic meningitis occurs in up to 15% of cases. In fact, mumps was the most common cause of viral meningitis in the prevaccine era.
Interestingly enough—and this is a clinical pearl—mumps meningitis is associated with a lymphocytic pleocytosis (inflammatory cells in the cerebrospinal fluid) that is typical of viral meningitis, but with a low glucose level.
Most children with typical summertime enterovirus meningitis have normal or low-normal CSF glucose levels, typically around 40%–50% of peripheral glucose.
In contrast, those levels might be somewhere between 10% and 25% with mumps meningitis. A low CSF glucose level might make you think of bacterial meningitis, so again, it's important to rule that out in order to treat appropriately.
In Iowa thus far, the median patient age at onset is 22 years. About one-fifth of all the patients are currently attending college.
Of 1,201 patients for whom vaccine history was investigated, 51% had documentation of receiving two MMR doses, 12% one dose, and 6% no doses. (Information was not available for the other 31%.)
It's not clear why immunized individuals would be contracting mumps. Although waning immunity may be a factor, in highly vaccinated populations a majority of individuals affected by a typical measles outbreak may represent vaccine nonresponders. This observation in the past led to the recommendation for two doses of MMR to be given.
Although a second dose can be given 30 days after the first, we currently give the second dose when a child starts school, potentially leaving the 1- to 5-year-old population vulnerable. Time will tell whether this age group emerges as a high-risk group.
In Iowa, the most common symptoms were parotitis in 60%, sore throat in 50%, submaxillary/maxillary gland swelling in 41%, and fever in 31%. Another 27% had headache, 9% cough, and 6% orchitis; 0.2% (3 patients) had encephalitis. Average duration of symptoms was 5 days.
In the prevaccine era, as many as 50% of postpubertal males with mumps developed testicular inflammation and 5% of postpubertal females developed ovarian inflammation, which may be confused with appendicitis. It's not clear why more cases of those complications haven't been reported in Iowa, although it's possible the information simply hasn't been sought.
Since mumps is self-limited, there's not much we can do as clinicians other than to make sure that our patients—as well as ourselves and our staffs—have received two doses of the MMR vaccine.
One dose of MMR is said to be 97% effective against mumps, but immunogenicity studies vary and some suggest that a single dose may protect 85%. A second dose may bring the protection rate to 90% or more. Vaccine immunity probably doesn't last more than 25 years. Mumps is similar in transmissibility to influenza and rubella, but less so than either measles or varicella.