Mumps

Mumps is symptomatic in 80% of infections (CDC, 2012), the main symptom being parotitis.

Risk of complications

The principal complications with mumps are orchitis, oorphoritis, meningitis, pancreatitis, and encephalitis.

Epididymo-orchitis occurs in 15–30% of adult men with mumps infection, but it is rare before puberty (Hviid, 2008). Oophoritis (ovarian inflammation), the counterpart of orchitis in females, is associated with pelvic pain and tenderness. It occurs in 5% of post-pubertal females (CDC, 2009).

Mumps meningitis is a benign entity with no significant risk of mortality or long-term sequelae. Even though cerebrospinal fluid pleiocytosis occurs in about half of the patients with mumps, clinical manifestations of meningitis arise in 1–10% of the cases (Hviid, 2008), and long-term morbidity is rare. Encephalitis occurs in 0.1% of acute cases (Hviid, 2008).

Acute pancreatitis, with symptoms of abdominal distention and pain, fever, nausea, and vomiting (Demirci, 2011), occurs in approximately 4% of mumps cases (Vanlioglu & Chua, 2011).

With mumps, the acute complications of symptomatic infections are considered as a single health state (complicated) because they can occur concomitantly.

Of all mumps infections, 40–50% may have only non-specific or primarily respiratory symptoms (CDC, 2012). Therefore, knowing that 20% of infections are asymptomatic, 32–40% of symptomatic cases were considered to be uncomplicated. Durations were set to 7–10 days for the uncomplicated cases and 7–14 days for the complicated ones.

Permanent deafness caused by mumps occurs with an estimated frequency of one in 20 000 cases (0.005%) and in 80% of the cases, hearing loss is monolateral (Hviid, 2008).

Case fatality proportion

Death is very rare in mumps cases and the mortality rate following encephalitis is 1.5%. Therefore, 0.0015% was used in the model for the risk of death resulting from all symptomatic infections. More than half of fatalities occur in patients over 19 years (Hviid, 2008; Demirci, 2011). This age distribution also applies to the symptomatic complicated cases (see Table 3).

Model input summary

Table 1. Transition probabilities used in the outcome tree

Health outcome
(Health state)

Distribution of health states in health outcome

Transition probability

Source/assumption

Symptomatic infection

(Uncomplicated)

(Complicated)

 

32–40%

60–68%

 

 

 

CDC, 2012

Permanent disability
due to hearing loss

 

0.005%

Hviid, 2008

Fatal cases

 

0.0015%

Age dependent
(see Table 3)

Hviid, 2008

Assuming 1.5% of encephalitis cases (0.1%) become fatal

Table 2. Disability weights and duration

Health outcome
(Health state)

Disability Weight (DW) (Haagsma, 2015)

Duration

DW

Label

In years

Source

Symptomatic infection

Uncomplicated

Complicated

0.051 (0.039-0.06)

0.125 (0.104-0.152)

Infectious disease, acute episode, moderate

Infectious disease, acute episode, severe

0.019-0.027

0.019-0.038

Hviid, 2008

Permanent hearing loss

0.008 (0.005-0.012)

Unilateral hearing loss

Remaining life expectancy

Hviid, 2008

Table 3. Age distribution – case fatality ratio

Age

%

0-19

50

≥20

50

References

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

Demirci CS, Abuhammour W, Quintana EC, Shahidi H, Wilkes G. Mumps. Available from http://emedicine.medscape.com/article/966678-overview [accessed 12 September, 2011].

Haagsma JA, Maertens de Noordhout C, Polinder S, Vos T, Havelaar AH, Cassini A, Devleesschauwer B, Kretzschmar ME, Speybroeck N, Salomon JA. Assessing disability weights based on the responses of 30,660 people from four European countries. Population Health Metrics 2015; 13: 10

Hviid A, Rubin S, Mühlemann K. Mumps. Lancet. 2008 Mar 15;371(9616):932-44.

Mandell GL, Bennet JE, Dolin R. Mandell, Douglas and Bennett’s Principles and Practice of Infectious Disease 5th edition. Churchill Livingstone, 1999.

Vanlioglu B, Chua TC. Presentation of mumps infection as acute pancreatitis without parotitis. Pancreas. 2011 Jan;40(1):167-8.