Mumps

Background

Mumps is a disease resulting from infection by the mumps virus. The disease is characterised by swelling of one or both cheeks or sides of the jaw, also known as parotitis, along with:

  • fever
  • headache
  • swollen glands

Mumps infection can also lead to serious complications including:

  • aseptic meningitis
  • encephalitis
  • inflammation of the testes
  • pancreatitis
  • oophoritis
  • permanent deafness

The most effective strategy for preventing the transmission of mumps is vaccination with the measles mumps rubella (MMR) vaccine.

More information on mumps can be found on the NHS inform website.

Guidance

Guidance on mumps: risk in pregnancy, infection in healthcare settings and the MMR vaccine can be found on the Public Health England website.

For all infection prevention and control guidance visit the A-Z ‚Äčpathogens section of the National Infection and Prevention Control Manual.

Data and surveillance

Surveillance update for April to June 2020

Mumps was a common childhood disease before the introduction of the MMR vaccine, with more than 85% of adults having evidence of previous mumps infection. Following the introduction of the MMR vaccine in 1988, the incidence of mumps substantially decreased. However, since 2004, there has been ongoing widespread increased incidence of mumps throughout the UK, with the number of laboratory-confirmed cases peaking in 2005. As shown in Figure 1, smaller outbreaks have occurred in 2009, 2012, and 2014 to 2015. At these points in time, most of the individuals affected were adolescents and young adults and had not received two doses of MMR.

Figure 1: Number of laboratory-confirmed cases of mumps in Scotland by year, 2000 to 2020 (to week 26)

Figure 1 is a line chart showing the number of laboratory-confirmed cases of mumps by year from 2000 to 30 June 2020. The figure shows the outbreak which started in 2004 and peaked in 2005 with 1,892 and 2,586 cases, respectively. While the number of cases has decreased since 2005, smaller outbreaks have occurred in 2009, 2012, and 2014 to 2015. The graph shows cases increasing again after 2016 with a total of 784 laboratory-confirmed cases of mumps reported in  2019, and 863 in the first six months (January to June) in 2020.

As shown in Figure 2, the number of laboratory-confirmed mumps cases has been variable over the last several years. Numbers by the end of 2019 reached 784, and the number of cases reported for 2020, by the end of March, was 853, exceeding the total for the previous year. In late 2014 to 2015, a widespread outbreak occurred which mainly affected those in higher education. The observed increase in cases in 2019 may represent poor initial immune response to the mumps component of the MMR vaccine, waning immunity, or a combination of both within fully and partially vaccinated individuals. From April this year there has been a notable drop in cases of mumps reported

Figure 2: Number of laboratory-confirmed cases of mumps in Scotland by month and year, 2015 to 2020 (to week 26)

Figure 2 is a bar chart showing the number of laboratory-confirmed cases of mumps by month and year from 2015 to 30 June 2020. The graph shows recurring peaks in the number of mumps cases reported by month, with the highest peaks occurring in June 2015 (142 cases), November 2017 (122 cases), April 2019 (119 cases) and December 2019 (109). The chart shows a sharp rise in cases at the start of 2020; 316 cases in January, 343 in February and 194 in March, however in the most recent three months, the number of cases can be seen to have dropped to 0 cases in June 2020.

There were 281 laboratory-confirmed mumps cases in 2018, which is a decrease compared to 2017 during which 385 cases were reported. In 2019, 784 laboratory-confirmed mumps cases were reported. NHS Boards continue to experience clusters of mumps which occur mainly in adolescents and young adults, with 853 cases reported in the first quarter of 2020. This trend has shown a significant decline, with only 10 cases reported between April and June this year. This is most likely to be the result of social distancing measures implemented to mitigate the transmission of COVID-19, which is likely to have also interrupted the transmission of mumps as well as reducing attendance at primary care to diagnose.

Age distribution of cases

Figure 3 shows that the majority of mumps cases in recent years have been in those aged between 17 to 34 years. Although the vaccination status of cases is not routinely collected, this is consistent with the age groups which are likely to be under-immunised with a mumps-containing vaccine, or for whom there is waning immunity.

Figure 3: Number of laboratory-confirmed cases of mumps in Scotland by age group and year, 2015 to 2020 (to week 26)

Figure 3 is a bar chart showing the number of laboratory-confirmed cases of mumps by age group and year from 2015 to 30 June 2020. While the overall number of cases varies by year, the majority of mumps cases in all years have occurred in individuals aged 17 to 34 years.

The incidence of mumps by age group in the first half of 2020, shown in Figure 4, reflects notably higher incidence among individuals aged 17 to 20 years compared to other ages (137 cases per 100,000 population). This was followed by those aged 21 to 24 years (88 cases per 100,000 population).

Figure 4: Number of laboratory-confirmed cases of mumps by age group, 2020 (to week 26)

Figure 4 is a bar chart and shows the incidence per 100,000 population of laboratory-confirmed cases of mumps by age group between 1 January and 30 June 2020. the incidence of mumps was highest among individuals aged 17 to 20 years, at 137 cases per 100,000 population. This was followed by those aged 21 to 24 years, at 88 cases per 100,000 population.

Laboratory confirmed cases by NHS boards

Figure 5 shows the variability in the incidence of mumps between NHS board. The highest incidence between January and June in 2020 was observed in NHS Forth Valley (48 cases per 100,000 population), followed by NHS Borders and Lothian (34 and 25 cases per 100,000 population, respectively).

Figure 5: Incidence of mumps cases per 100,000 population by NHS board, 2020 (to week 26)

Figure 5 shows the incidence per 100,000 population cases of mumps by NHS Board between 1st January and 30 June 2020 as a bar chart. During this period, the incidence of mumps was highest NHS Forth Valley (48 cases per 100,000 population), followed by NHS Borders and Lothian (34 and 25 cases per 100,000 population, respectively).

Limitations

There are limitations caused by a reliance on laboratory reports as this will represent a considerable underestimate of community circulation of mumps as many cases may be undiagnosed or based on clinical confirmation only.  It should also be noted that differences in sampling and testing practices may account for variation across the NHS boards.

Vaccination

Vaccine uptake statistics are published by Public Health Scotland Data and Intelligence.