Infectious diseases in children: Mumps

The effectiveness of modern immunisations and vaccination programmes means that many of the childhood diseases that used to be common are now seldom seen, and when they present, they may not be immediately recognised. And it is easy to forget that many childhood illnesses can be dangerous, as the recent pertussis epidemic has so graphically illustrated. In this series, we look at the diseases, how to prevent them, how to recognise them and how to manage them when they do occur

WHAT IS MUMPS?

Mumps is a contagious viral disease, which primarily causes a marked parotitis but which can occasionally cause painful orchitis, rarely causes meningo-encephalitis and even more rarely cause permanent deafness. It remains a notifiable disease monitored by WHO.¹

SPREAD

Mumps is caused by a paramyxovirus, and is spread by nasal droplet infection. It has a long incubation period (15-24 days) and once clinical infection is present patients remain infectious for a week or so. Infection is more common in winter and spring.

INCIDENCE AND PREVALENCE

In the UK

Prior to the introduction of the MMR vaccine, mumps infection was almost universal in childhood. Incidence fell rapidly after the introduction of routine vaccination in October 1988.

Since 1996, a second dose of MMR has been offered pre-school.

We now see 2000 — 3000 cases a year, although there was an outbreak in 2005 (see Box 1).

Across the world

Mumps is still a significant threat to health in the developing world.

WHO maintains a table of numbers of notified cases in every country.¹ China had nearly half a million notified cases in 2011.

DIAGNOSIS

Mumps is suspected on clinical grounds. However, the UK Health Protection Agency (HPA) recommends lab testing of blood or saliva for confirmation. Diagnosis on solely clinical grounds is less trustworthy when a disease is less common, because the likelihood of the correct diagnosis being something else becomes relatively greater, plus our experience and knowledge fade. Of course, during an epidemic diagnosis on clinical grounds may suffice as in an epidemic, things that look like mumps generally are mumps.

The differential diagnosis for parotitis includes other viral, bacterial or tuberculous parotitis, Sjogrens syndromes, parotid stones, and glandular fever. There are many differential diagnoses for ovarian and testicular pain, for fever and for malaise, and for meningeal symptoms the differential includes meningococcal disease.

SIGNS AND SYMPTOMS

Mumps is usually a mild and self-limiting disease, although it can be unpleasant. Serious consequences are possible, though rare.

The main symptom is parotitis, found in around 95% of symptomatic patients — although most begin with fever, malaise and sometimes a blotchy red rash. Initially there is unilateral parotitis, although 90% progress to bilateral parotitis. The glands are tender, and pain occurs on chewing. Fever usually settles by day four and symptoms overall last about a week. Up to 30% of cases may be asymptomatic.

Mumps may cause a mild pancreatitis, as the exocrine pancreas is essentially a type of salivary gland, and the mumps virus likes salivary glands.

Meningeal signs of headache, photophobia, vomiting and neck stiffness occur in about 1 patient in 10, and there is laboratory evidence of meningeal inflammation in about half of infected patients. Before the introduction of MMR, mumps was also the commonest cause of viral encephalitis, although it occurs in less than 2 per 100,000 cases.

Although very unpleasant, mumps meningo-encephalitis is usually self-limiting over a few days with no permanent sequelae.

The most famous complication of mumps is orchitis. It is uncommon in prepubertal boys, and is usually unilateral when it does occur, so subsequent infertility, much feared, is in fact very unusual. It is nevertheless painful, and about 1 in 4 men over 12 who develop mumps will experience orchitis.

Other rare symptoms of mumps include ovarian inflammation, mastitis and arthritis, loss of voice or hearing. All are usually transient — although rarely permanent hearing loss can result.

Mumps in the first trimester of pregnancy is associated with a risk of miscarriage, although it does not appear to cause defects or malformations in the baby in those pregnancies that continue to term.

MANAGEMENT

Treatment is symptomatic while waiting for the virus to run its course. Simple painkillers are used to treat pain and children are generally kept off school until they are well again.

Parotitis may be relieved by applying of intermittent ice or heat to the affected area. Warm salt water gargles, soft foods, and extra fluids may also help relieve symptoms.

Patients are advised to avoid acidic foods and beverages, since these stimulate the salivary glands, which can be painful. After recovery, immunity is lifelong although very mild reinfection can occur.

PREVENTION AND IMMUNITY

The main preventative measure is the vaccine, given in the UK since 1988 as a part of MMR. (In the US, MMR vaccination began in 1967 and is now supplanted by MMRV which adds varicella vaccine.)

In the UK, MMR is routinely given at age 13 months with a booster at 3—5 years. This confers lifelong immunity with an efficacy of around 80%. Some anti-vaccine activists suggest that the vaccine is harmful, and/or that the wild disease is beneficial. There is no evidence to support this. Claims were also made linking MMR vaccine to autism and inflammatory bowel disease, centred around a study by Andrew Wakefield. This paper was discredited and retracted in 2010 and Wakefield was later struck off the medical Register after his work was held to be fraudulent. The detail of the judgment of his actions makes shocking reading.²

SUMMARY

Mumps is uncommon, but not rare. It can be unpleasant but rarely has serious consequences. The practice nurse should be alert to suspect it, particularly where unwell children have a swollen face or pain on chewing, and should seek to confirm diagnosis by serology.

• Next time — Rotavirus.

REFERENCES

1. WHO. Mumps reported cases http://apps.who.int/immunization_monitoring/en/globalsummary/timeseries/tsincidencemum.htm

2. Exposed: Andrew Wakefield, The Fraud Investigation: http://briandeer.com/mmr/lancet-summary.htm