April 4, 2006 -- Iowa is experiencing an epidemic of mumps, a viral infection usually made rare by vaccination.
Iowa's public health department reports 300 confirmed, probable, or suspected cases of mumps through April 3.
That's a "dramatic increase," Iowa public health officials say in a letter to Iowa health care facilities. Since 2001, the U.S. has averaged 265 mumps cases per year, with five of those cases in Iowa, according to the CDC.
"We don't know why this is occurring," CDC spokeswoman Lola Russell tells WebMD. The CDC is investigating the epidemic, Russell says.
The CDC's Morbidity and Mortality Weekly Report, published on March 28, also notes 14 possible mumps cases in three neighboring states (11 in Illinois, two in Nebraska, and one in Minnesota).
Health officials recommend that people complete their two regular doses of the measles-mumps-rubella (MMR) vaccine. Iowa patients are also being asked to isolate themselves for five days after symptoms start, but Iowa isn't quarantining people who may have been exposed to mumps.
"Permanent, long-term health impacts from mumps, while they can occur, are rare. Most people get over mumps with no problems after a couple of days of home rest," Russell says.
Mumps in Iowa
Iowa's strain of mumps isn't rare, according to the web site of Iowa's public health department. The same strain was seen in a mumps outbreak in the U.K. that peaked in 2005, Russell says.
Mumps-like illness was seen in December 2005 at an unnamed university in eastern Iowa. Several students with swollen glands were screened for mumps; two tested positive, the CDC states.
Another case from an unrelated Iowa patient was seen in January 2006. By mid-February, experts were watching out for mumps in seven Iowa regions, including at the state's three largest universities.
Iowa patients were about 21 years old, on average. About 20% were college students.
Vaccinated or Not?
Iowa's public health department reports that the vaccination records of 163 mumps patients have been investigated.
Of those patients, more than two-thirds (68%) had gotten two doses of the MMR vaccine, 13% had gotten one dose, 5% had gotten no doses, and 15% had uncertain vaccine status, states the CDC.
In 1977, Iowa required one dose of the MMR vaccine for all children entering public schools. That requirement rose to two doses in 1991.
"Mumps should not be ruled out in someone who is vaccinated if they have symptoms clinically consistent with mumps," Iowa public health officials wrote in their letter to the state's health care facilities.
However, Iowa's health department still recommends MMR vaccination for all susceptible people. "The MMR vaccine is 95% effective," Russell says.