The word is generally therefore sometimes it is not mild, why cant you understand that.Nobody said it was a leading cause of death, but it did cause death and disablilty ie deafness and the consequences of encephalitis and subfertility.
From the IOM book i have looked to above and many times before
" 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)."
From the encephalitis society
"Mumps virus frequently infects the central nervous system. Before the MMR vaccine was introduced mumps used to be the most common cause of admission to hospital with Meningitis or Encephalitis, occurring in 1 in 200- 1 in 5,000 children. Mumps also causes deafness. MMR vaccine has had a dramatic impact and hardly any children are admitted to hospital with mumps these days. Outbreaks of mumps have occurred in recent years in older children and young adults who were too old to have received the two doses of MMR vaccine recommended before going to school."