ted by direct contact with infectious respiratory secretions, droplet nuclei, or fomites that are then transferred to the nose and mouth (Litman and Baum, 2010).
The average incubation period of the mumps virus is 16 to 18 days but can range from 2 to 4 weeks (Litman and Baum, 2010). Fifteen to 20 percent of mumps infections are asymptomatic; 50 percent of cases have nonspecific symptoms such as anorexia, headache, fever, and malaise, or present primarily as respiratory infections; and only 30 to 40 percent demonstrate the classic salivary gland tenderness and enlargement (parotitis) (CDC, 1998). Asymptomatic infection is more common in adults, while parotitis occurs most often in children age 2 to 9 years (CDC, 1998). Children younger than 5 years old more commonly manifest symptoms of lower respiratory disease (Plotkin and Rubin, 2008). Complications of mumps infection are possible without the presence of parotitis. In 1958, Philip et al. (1959) observed testicular and mammary inflammation in 5 percent of postpubertal men and 31 percent of women over 15 years of age. Pancreatitis occurs in 4 percent of cases, and although it has not been proven, evidence suggests an association between mumps infection and diabetes mellitus (Sultz et al., 1975). Neurological complications are more common in adults and occur three times more often in men than in women (Plotkin and Rubin, 2008). These complications include mumps meningitis, cerebellar ataxia, transverse myelitis and poliomyelitis-like disease, cranial nerve palsies, hydroencephalitis, and encephalitis, which occurs in less than 0.3 percent of cases, but is responsible for more than 50 percent of mumps-related fatalities (Bray, 1972; Cohen et al., 1992; Kilham et al., 1949; Lahat et al., 1993; Oldfelt, 1949; Oran et al., 1995; Plotkin and Rubin, 2008; Timmons and Johnson, 1970). Hearing loss due to infection of the endolymph is also a potential complication of mumps infection (Tanaka et al., 1988). Short-term, high-frequency deafness occurs in approximately 4 percent of mumps cases, and permanent hearing loss occurs in only 1 per 20,000 cases and is usually unilateral (Litman and Baum, 2010; Plotkin and Rubin, 2008). Mumps arthropathy, more common in men than women, occurs most often in young adults (Plotkin and Rubin, 2008). It may manifest as arthralgias, polyarticular migratory arthritis, and monoarticular arthritis (Gordon and Lauter, 1984; Harel et al., 1990). Myocarditis is rare and generally self-limited, although some fatal cases have been reported (Chaudary and Jaski, 1989; Roberts and Fox, 1965).
Johnson and Goodpasture (1934) identified the causative agent of mumps in 1934, and in 1945 Habel and Enders successfully cultivated the virus in chick embryos (Enders, 1946; Habel, 1945). The first inactivated mumps vaccine was developed in 1946 and tested in humans in 1951 (Habel, 1946, 1951). The first live, attenuated vaccine was developed in the 1960s in the United States and former Soviet Union (Plotkin and Rubin,