Since 2001, there was an average of five mumps cases per year in Iowa and 265 cases nationally (Quinlisk et al 2006). However, there were 219 cases reported in Iowa from December 2005 through March 2006, and by October there was a total of 1,964 cases. Nationally, there were 6,584 cases by the end of the outbreak (Quinlisk et al 2006 and Dayan et al 2008). The outbreak spread to 45 states. Neighboring Midwestern states were the most affected. These states were Illinois, Iowa, Wisconsin, Minnesota, Nebraska, South Dakota, Kansas, and Missouri (Dayan et al 2008). The outbreak was characterized by the high rate of affected college student population with 84% of cases between ages of 18-24 and 83% of those enrolled in college. Also, there was a high 2-dose Measles Mumps and Rubella (MMR) vaccination rate among those infected with 63% of total cases and 84% of cases between the ages of 18-24(Dayan et al 2008). Mumps is an acute viral infection that is transmitted through contact with salivary gland secretions and airborne, such as coughing and sneezing (Quinlisk et al 2006, Dayan et al 2008, Parker Fiebelkorn et al 2012, and IDPH 2012).
Case reporting occurs on three different levels of public health – local, state, and national. The 2006 mumps outbreak investigation began at the state level. The Iowa Department of Public Health (IDPH) led the investigation using a passive surveillance strategy (Quinlisk 2010).
Mumps is a reportable disease condition in the state of Iowa. Hospitals, clinics, and laboratories have three days to report a positive diagnosis of mumps (IDPH 2012). . A mumps case can be diagnosed either by a positive laboratory test or meet the clinical definition. The clinical case definition of mumps is “an illness with acute onset of unilateral or bilateral tender, self-limited, swelling of the parotid or other salivary gland, lasting 2 or more days, and without other apparent cause”(IDPH 2012 and Gershman et al 2006). The cases identified in December 2005 appeared routine at first. However, in January 2006, the cases met the definition of a mumps outbreak, which is an epidemiological linkage between three or more cases (Quinlisk 2010 and Parker Fiebelkurn et al 2012).
Public health laboratories rely on two main tests to confirm a mumps case. The first is a serological test for mumps virus IgM. The serological test requires a blood sample. This sample is collected at the clinic (Parker Fielbelkurn et al 2012 and IDPH 2012). Throughout the 2006 outbreak, the viral isolates from the serological tests were sent to the CDC. The CDC identified the strain as genotype G (Quinlisk et al 2006). All cases in the multi-state outbreak were identified from the same strain, genotype G (Dayan et al 2008).
In addition to serological testing, the mumps virus can be detected in a real time polymerase chain reaction (RT PCR) test using a M4 viral transport medium (Parker Fiebelkurn et al 2012 and IDPH 2012). This method was developed during the...