Vaccine Preventable Diseases in Australia, 2005 to 2007

3.8 Mumps

Page last updated: 24 December 2010

Mumps is an acute viral disease caused by a paramyxovirus. The classical disease is characterised by fever, as well as swelling and inflammation of one or more salivary glands, most commonly the parotid glands. However, up to 30% of cases will not have salivary gland involvement. It is a multi-system infection, with up to 10% of cases developing aseptic meningitis and 30% of post-pubertal males experiencing epididymo-orchitis.1

Case definitions

Notifications

See Appendix 6.6 for pre-2004 definition

National definition from January 2004:2

Only confirmed cases are notifiable. Confirmed cases require either laboratory definitive evidence, or laboratory suggestive evidence and clinical evidence, or clinical evidence and an epidemiological link to a laboratory-confirmed case.

  1. Laboratory definitive evidence
    • Isolation of mumps virus; or
    • Detection of mumps virus by nucleic acid testing; or
    • IgG seroconversion or a significant increase in antibody level or a 4-fold or greater rise in titre to mumps virus in the absence of recent vaccination.
  2. Laboratory suggestive evidence
    • Detection of mumps-specific IgM antibody in the absence of recent vaccination.
  3. Clinical evidence
    • A clinically compatible illness characterised by swelling of the parotid or other salivary glands lasting 2 days or more without other apparent cause.

Hospitalisations and deaths

The ICD-10-AM/ICD-10 code B26 (mumps) was used to identify hospitalisations and deaths.

Top of page

Secular trends

The epidemiology of mumps in Australia during this reporting period was characterised by a substantial increase in notifications in the latter half of 2007. This resulted particularly from outbreaks of mumps around two Indigenous communities in the Northern Territory, together with increased notifications from Western Australia (where some of the cases were linked to the Northern Territory outbreaks) and, to a lesser extent, New South Wales. Those affected were predominantly young adults and adolescents.

Figure 3.8.1: Mumps notifications and hospitalisations, Australia,* 1993 to 2007, by month of diagnosis or admission

Figure 3.8.1:  Mumps notifications and hospitalisations, Australia, 1993 to 2007, by month of diagnosis or admission

* Note that the number of jurisdictions notifying mumps increased over the review period until July 1996 when mumps became notifiable in all states and territories. From July 1999 until June 2001, mumps was not notifiable in Queensland. Only the Australian Capital Territory, New South Wales and Victoria notified for the entire review period.

† Notifications where the date of diagnosis was between January 1993 and December 2007; hospitalisations where the date of admission was between July 1993 and June 2007.

Top of page

During the 2 years from January 2006 to December 2007, there were 857 notifications of mumps (an average annual notification rate of 2.1 per 100,000) (Table 3.8.1). Although 2006 continued the recent trend of increasing notifications (275 notifications, rate 1.3 per 100,000), it was 2007 that was particularly remarkable with 582 notifications, at a rate of 2.8 per 100,000. To put this in perspective, there were 163 more notifications in 2007 alone than in 2003–2005 combined, and the notification rate in 2007 was about 4 times the average annual rate for 2003–2005.3 The median number of notifications per month during the period from January 2006 to April 2007 was 19 (range 7–37) with the peak in July 2006, in contrast to 55 per month (range 33–104) from May to December 2007 with the peak in November 2007 (Figure 3.8.1). It is generally recognised that the peak incidence of mumps in temperate climates typically occurs in winter and spring. This pattern has largely been maintained during the 2006–2007 period with the number of cases during the winter and spring months being either close to the median or well above it.

From July 2005 to June 2007, there were 107 hospitalisations coded as being due to mumps (average annual rate of 0.26 per 100,000), of which 94 (88%) had mumps listed as the principal diagnosis (Table 3.8.1). During this period there was a median of 4 admissions per month (range 0–11), compared with a median of 3.5 admissions per month in the preceding 2-year period.3 Seventy-five of the 107 hospitalisations occurred in the 12 months from July 2006 to June 2007, with a median of 6 admissions per month (range 0–11) during this period, compared with a median of 3 admissions per month (range 1–6) from July 2005 to June 2006. At the time of preparation of this report, hospitalisation data for the latter half of 2007, when there was a substantial increase in mumps notifications, were not yet available for comparison. During the period when data are available for both, hospitalisation rates mirrored the fluctuating trends in notification rates (Figure 3.8.1) on a much smaller scale.

Table 3.8.1: Mumps notifications, hospitalisations and deaths, Australia, 2005 to 2007,* by age group

Age group
(years)
Notifications
2 years
(2006–2007)
Hospitalisations
2 years
(July 2005–June 2007)
LOS per admission
(days)
Deaths
2 years
(2005–2006)
n Rate n (§) Rate (§) Median (§) n Rate
0–4
19
0.7
9
(9)
0.35
(0.35)
1.0
(1.0)
0
5–14
95
1.7
14
(13)
0.26
(0.24)
1.0
(1.0)
0
15–24
200
3.4
19
(18)
0.33
(0.32)
1.0
(1.0)
0
25–59
525
2.6
52
(46)
0.26
(0.23)
1.5
(1.0)
0
60+
18
0.2
13
(8)
0.18
(0.11)
6.0
(5.5)
1
0.01
All ages
857
2.1
107
(94)
0.26
(0.23)
1.0
(1.0)
1
<0.005

* Notifications where the date of diagnosis was between January 2006 and December 2007; hospitalisations where the date of separation was between July 2005 and June 2007; deaths where the death was recorded between January 2005 and December 2006.

† LOS = length of stay in hospital.

‡ Average annual age-specific rate per 100,000 population.

§ Principal diagnosis (hospitalisations).

Top of page

Severe morbidity and mortality

There were 343 hospital bed days (average 171.5 per year) recorded for patients with an ICD-10-AM code for mumps. Complications arising from mumps infection were recorded for 22 hospitalisations (20.6%). As in the past, the most commonly reported complication was orchitis. There were 14 (13%) hospitalised cases coded with orchitis; 13 of these were between 15 and 59 years of age (Table 3.8.2). There were 2 hospitalisations coded as neurological complications (encephalitis or meningitis) and 1 as pancreatitis, all of which occurred in cases aged 15–59 years. Five patients were listed as having ‘other complications’; unfortunately, these are not specified. As with the neurological complications and orchitis, nearly all the cases with ‘other complications’ occurred in the adolescent and adult age groups. None of these hospitalisations had multiple mumps complication codes. The median length of stay in hospital was 1 day, but adults aged ≥25 years had a longer median LOS compared with younger age groups (Table 3.8.1), especially cases aged ≥60 years who had a median LOS of 6 days. Adults in the 25–59 years age group (which constitute about 49% of the Australian population) accounted for 48.6% of the hospitalisations, compared with 38.4% during the preceding 3-year period.3 Adults over 15 years of age (constituting about 80% of the total population) accounted for 78.5% of hospitalisations, which was not substantially different from the figure in the preceding 3 years of 75.4%.3 Mumps was recorded as the underlying cause of death in one adult (aged ≥60 years) in the period 2005–2006 in the AIHW National Mortality Database.

Table 3.8.2: Indicators of severe morbidity* for hospitalised cases of mumps, Australia, 2005 to 2007,* by age group

Age group
(years)
Mumps meningitis or encephalitis Mumps
orchitis
Mumps
pancreatitis
Mumps with
other complications
n % Total n % Total n % Total n % Total
0–4
0
1
11.1
0
0
5–14
0
0
0
1
7.1
15–24
1
5.3
2
10.5
0
0
25–59
1
1.9
11
21.2
1
1.9
2
3.8
60+
0
0
0
2
15.4
All ages
2
1.9
14
13.1
1
0.9
5
4.7

* Based on National Hospital Morbidity data where the date of hospital separation was between July 2005 and June 2007.

† % of total in the age group.

Top of page

Age and sex distribution

Since 2002, relatively low notification rates have continued in the 0–4 years and the ≥35 years age groups. Since 2005, there have been progressive increases in notification rates for most age groups, compared with 2002–2004, particularly in those aged 15–34 years. The increases in notification rates were most notable in 2007, and affected all age groups (Figure 3.8.2). The majority of notifications in 2006–2007 occurred in the 15–34 years age group. The proportion of the total notifications accounted for by this age group, who constituted approximately 28% of the total Australian population, has increased from 50.4% of the total (211/419) during 2003–2005 to 63.4% of all cases (543/857) in the 2006–2007 period.

Figure 3.8.2: Mumps notification rates, Australia, 1999 to 2007,* by age group and year of diagnosis

Figure 3.8.2:  Mumps notification rates, Australia, 1999 to 2007, by age group and year of diagnosis

* Notifications where the date of diagnosis was between January 1999 and December 2007.

Top of page

Hospitalisation rates in 2005/2006, compared with the previous 3 years, were lower for those aged 15–24 years and ≥35 years, and were comparable among other age groups. However, in 2006/2007, there was an increase in the hospitalisation rates for all age groups, in particular those aged 15–34 years, compared with 2005/2006 (Figure 3.8.3). Over the 2-year period between July 2005 and June 2007, the highest hospitalisation rates were observed in those aged 25–29 years (0.54 per 100,000) and 30–34 years (0.46 per 100,000). The overall male:female ratio was 1.2:1 for notifications and 1.7:1 for hospitalisations over the 2-year review period. The male predominance in notification rates occurred mainly in those aged 20–39 years, with a male:female ratio of 1.3:1 (ranging from 1.2:1 in those aged 25–29 years to 1.6:1 in those aged 20–24 years).

Figure 3.8.3: Mumps hospitalisation rates, Australia, 1998/1999 to 2006/2007,* by age group and year of separation

Figure 3.8.3:  Mumps hospitalisation rates, Australia, 1998/1999 to 2006/2007, by age group and year of separation

* Hospitalisations where the date of separation was between July 1998 and June 2007.

Top of page

Geographical distribution

The Northern Territory reported a mumps notification rate of 27.0 per 100,000 in 2007, which was dramatically higher than any of the other states or territories over the 2-year period, although it only accounted for 10% of the total notifications in 2007 (58/582). On a lesser scale, Western Australia also experienced a marked increase in the notification rate in 2007 of 5.2 per 100,000 compared with 0.8 per 100,000 in 2006. New South Wales accounted for the bulk of the notifications in 2006–2007 with 478 cases (55.8%), at an increased rate in 2007 (4.7 per 100,000) compared with 2006 (2.3 per 100,000) and 2005 (1.6 per 100,000) (Appendix 6.2).

In Western Australia, the majority of mumps notifications in 2007 were teenage and young adult Aboriginal people living in the Kimberley region, epidemiologically linked to a mumps cluster in the Northern Territory.4,5 Among notified mumps cases in Western Australia between July 2007 and June 2008 that occurred or were epidemiologically linked to the Kimberley region (which comprised 84% [153/183] of all notified cases in this state during this period), 92% were Indigenous Australians. Most of these mumps patients (82%; 126/153) were aged 5–29 years, with 22% (34/153) aged 15–19 years. Among the Kimberley Indigenous population, notification rates were highest in those aged 15–19 years, with a rate of 1,816 per 100,000 population.5 In the Northern Territory in 2007, despite notifications being found territory-wide, highest notification rates occurred within two geographically defined communities and their outstations, at a remarkable rate of 3,700 per 100,000. Over 90% of notifications in the Northern Territory were in Indigenous people, with the majority occurring in the 15–19 years age group.6

Thirty-two notifications of mumps during 2006–2007 were acquired overseas (3.7%). The geographic origin of 76 notifications (8.9%) was unknown.

No cases were hospitalised in the Australian Capital Territory or the Northern Territory during the 2-year review period. The remaining states had similar hospitalisation rates, ranging from 0–0.2 per 100,000 in 2005/2006 and 0.1–0.5 per 100,000 in 2006/2007 (Appendix 6.3).

Top of page

Vaccination status

During the 2006–2007 period, there were 371 notifications of individuals born after 31 December 1980. Among the 357 cases who were aged ≥4 years (who would have received 2 doses of mumps-containing vaccine as per current recommendations), 111 (31%) were reported as ‘fully vaccinated’, 23 (6%) as ‘partially vaccinated for age’ and 102 (29%) as ‘unvaccinated’; vaccination status was unknown or missing for the remaining 121 cases (34%). The vaccination status was validated in only 92 (25%) of these 371 records. Of the 92 cases with vaccination status validated, 72 (78%) had been fully vaccinated, 16 (17%) partially vaccinated, 2 were unvaccinated and 2 had an unknown status.

The Northern Territory examined mumps notifications in the 2007 outbreak using an expanded ‘outbreak’ case definition. Of those in whom immunisation status could be verified, 12/61 (20%) were fully immunised and 31/61 (51%) were partially immunised. It is important to note that the definition for ‘partially immunised’ included those individuals who had received 2 doses of vaccine but with the first dose having been given under 12 months of age (21/31).6

Top of page

Comment

There was a considerable rise in mumps notifications during 2003–2005 and this trend has shown no indication of slowing over the 2006–2007 period; in fact, 2007 provided the largest number of annual notifications since mumps became notifiable in all states and territories in 1996.7

While higher rates of other vaccine preventable diseases have frequently been reported in Aboriginal and Torres Strait Islander people, this has rarely been the case for mumps until the dramatic increases in notification rates in the Northern Territory and Western Australia in 2007. This is likely to be multifactorial in origin with factors such as overcrowding and Indigenous-specific immunisation policies (see below).

Once again, almost 90% of notifications could be attributed to adolescents and adults. Those adults aged 20–34 years accounted for over 50% of cases. This finding comes in the light of recent data highlighting that many Australians born in the late 1970s and early 1980s are particularly susceptible to mumps due to not having received 2 doses of the vaccine. The recommendation arising from these data is that adults aged 25–30 years of age should receive a second dose of MMR vaccine at an opportune occasion, such as just prior to overseas travel.7

Despite the increase in notifications over 2006–2007, the rates of hospitalisation and documented complications of mumps seem to have remained fairly stable. This is somewhat surprising since severe complications of mumps, such as orchitis, can occur in up to 30% of post-pubertal males with the infection; however, it may be that such cases were managed in the outpatient setting and therefore not documented in hospitalisation data. Another plausible explanation is that mumps cases and the associated complications were never notified because they had not been identified. This is because the clinical case definition for mumps makes parotid or other salivary gland involvement mandatory; yet, paradoxically, 10%–30% of cases of mumps do not have the classical parotitis and therefore would not meet the clinical case definition and would not be reported unless there was laboratory confirmation or an epidemiological link to a confirmed case.1

Mumps continues to be a problem in other developed nations although notifications appear to be declining in the USA and the UK. In 2006 in the USA, over 5,000 cases of mumps were notified. Similar to Australia, adolescents and young adults were the age group predominantly infected in the USA with the highest age-specific rates occurring in the 18–24 years age group. Many of these were college students. The median age for mumps notifications in the USA in 2006 was 22 years.8 There was a marked decline in notifications in the USA in 2007.9 Although the reasons for this are not certain, it may partly reflect (particularly at a college level) a combination of fewer susceptible persons as a result of outbreaks over the previous years and increased immunisation among susceptible persons in response to these outbreaks. England and Wales have experienced a decline in mumps notifications in 2006 and 2007 with 4,420 and 1,476 confirmed cases (by laboratory reporting or detection of salivary IgM), respectively, following a peak of >43,300 cases in 2005. Mirroring the trend in Australia and the USA, the bulk of the notifications in England and Wales in 2006 and 2007 occurred in adolescents and young adults aged 15–24 years.10

Top of page

Despite the push to vaccinate those young adults who may only be partially immune to mumps, a worrying finding is that mumps cases are occurring even in those individuals who are fully vaccinated. In other words, it is not just an infection of those partially vaccinated or unvaccinated. At least 72 notifications in Australia over 2006–2007 occurred in these fully vaccinated individuals; the number may well be higher but the vaccination status of others was not validated and therefore cannot be reliably assessed. The Northern Territory data for mumps outbreaks in two communities in 2007 raise another important issue, namely the effect of the timing of childhood vaccination on the efficacy of the mumps vaccine. From 1984–1998 in the Northern Territory, Indigenous infants received their first dose of mumps vaccine at the age of 9 months, in contrast to non-Indigenous infants who received their first dose at 12 months of age. This policy was put in place to counter Indigenous children’s increased susceptibility to measles.11 In two Northern Territory communities that reported mumps outbreaks in 2007, 21/61 cases in whom the immune status was known occurred in individuals who had received 2 doses of mumps vaccine but with the first dose at <12 months of age. This raises the possibility that immunising infants against mumps with the first dose at age <12 months might have been less effective than immunising them for the first time at 12 months of age. In Western Australia in 2007, almost half of the notifications occurred in those who had been vaccinated twice.4 This pattern is not unique to Australia. Examination of mumps cases from Iowa in the USA in 2006 found that 49% of cases had received 2 or more doses of MMR vaccine, 14% had received 1 dose, while 30% had an unknown vaccination status.8 Even more strikingly, in a mumps outbreak in 2005–2006 in Czechoslovakia, 87% of 15–19 year old cases had received 2 doses of vaccine.12 The implication of these findings is that even ensuring that all susceptible individuals receive 2 doses of MMR vaccine is no guarantee of protection from mumps. There are potentially a number of reasons for appropriately vaccinated individuals developing mumps, namely administration of ineffective vaccine initially (e.g. by breaching the cold chain), waning immunity, and failure of cross-neutralisation between vaccine strains and wild-type genotypes.1

In Australia in 2006–2007, only about 4% of notified mumps cases were imported. This indicates that local transmission of mumps is well established in the community. However, the occurrence of imported cases indicates that mumps can be a travel-related infection, as can measles and meningococcal disease, especially for susceptible adolescents and young adults travelling overseas from Australia. These travellers can, in turn, infect other susceptible individuals on their return to Australia. Furthermore, it may be possible for a fully immunised traveller to be exposed to a strain of mumps overseas that will not induce cross-neutralisation with the local vaccine strain, thereby leading to clinical infection and infectivity.

One case of hospitalisation due to mumps orchitis was reported in a boy aged 0–4 years (Table 3.8.2). Although mumps orchitis is regarded as a manifestation of post-pubertal males, rare occurrences in young children have been reported.13

In summary, Australia has seen a large increase in mumps notifications, in 2007 in particular. Mumps has now become a disease primarily affecting adolescents and young adults, although all age groups are still affected. It also now appears that immunisation with 2 doses of childhood vaccine is not a guarantee of immunity, and a booster program targeting at-risk age groups needs to be considered. During late 2007, Indigenous communities in the Northern Territory and Western Australia experienced mumps outbreaks. These factors underline the importance of ongoing surveillance, including the Indigenous status and vaccination status of people reported with mumps, to enable monitoring of incidence in Indigenous populations and vaccine effectiveness in a range of settings.

Top of page

References

1. Senanayake SN. Mumps: a resurgent disease with protean manifestations. Med J Aust 2008;189(8):456–459.

2. Communicable Diseases Network Australia. Surveillance case definitions for the Australian National Notifiable Diseases Surveillance System. 2004. Available from: http://www.health.gov.au/internet/main/publishing.nsf/Content/cdna-casedefinitions.htm Accessed on 24 August 2009.

3. Brotherton J, Wang H, Schaffer A, Quinn H, Menzies R, Hull B, et al. Vaccine Preventable Diseases and Vaccination Coverage in Australia, 2003 to 2005. Commun Dis Intell 2007;31(Suppl):S1–S152.

4. Review of notifiable diseases, 2007. Vaccine preventable diseases. Disease Watch – the Western Australian Communicable Diseases Bulletin 2008;12(2):9–10. Available from: http://www.public.health.wa.gov.au/cproot/1397/2/DW%20%2012%20no%202%20Mar%202008vfinal_web.pdf Accessed on 11 May 2009.

5. Bangor-Jones RD, Dowse GK, Giele CM, Van Buynder PG, Hodge MM, Whitty MM. A prolonged mumps outbreak among highly vaccinated Aboriginal people in the Kimberley region of Western Australia. Med J Aust 2009;191(7):398–401.

6. Coleman K, Markey P, Krause V. Mumps in the NT. The Northern Territory Disease Control Bulletin 2008;15(4):11–17.

7. Aratchige PE, McIntyre PB, Quinn HE, Gilbert GL. Recent increases in mumps incidence in Australia: the “forgotten” age group in the 1998 Australian Measles Control Campaign. Med J Aust 2008;189(8):434–437.

8. Centers for Disease Control and Prevention. Brief report: update: mumps activity—United States, 1 January–7 October 2006. MMWR Morb Mortal Wkly Rep 2006;55(42):1152–1153.

9. Hall-Baker PA, Nieves E, Jr., Jajosky RA, Adams DA, Sharp P, Anderson WJ, et al. Summary of notifiable diseases – United States, 2007. MMWR Morb Mortal Wkly Rep 2009;56(53):1–94. Available from: http://www.cdc.gov/mmwr/PDF/wk/mm5653.pdf Accessed on 11 September 2009.

10. Health Protection Agency. Confirmed cases of mumps by age and region: 1996–2008. 2009. Available from: http://www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1195733841496 Accessed on 2 July 2009.

11. Miller N. Changes to the Northern Territory childhood vaccination schedule – MMR. The Northern Territory Disease Control Bulletin 1998;5(3):1–3.

12. Boxall N, Kubínyiová M, Príkazský V, Beneš C, Cástková J. An increase in the number of mumps cases in the Czech Republic, 2005–2006. Euro Surveill 2008;13(16):p11=18842. Available from: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=18842 Accessed on 5 March 2009.

13. Green GF. Mumps orchitis in childhood. Practitioner 1964;192:550–552.

Document download

This publication is available as a downloadable document.

Vaccine Preventable Diseases in Australia, 2005 to 2007(PDF 1217 KB)