Introduction
Mumps is a generalised infection caused by a paramyxovirus. It can affect any organ but classically mumps causes a large swelling of the parotid gland causing the characterised lump in the neck.
It has a relatively long incubation period of about 16-18 days. It is highly infectious and spread by droplets in close contact. It is most infectious from about 2 days before symptoms to 9 days afterwards. Asymptomatic infection infection is common – especially in children. Asymptomatic patients are often still infectious.
Since the introduction of vaccination (in 1987 in the UK) most cases are now in outbreaks in Universities. Cases are on the rise since the advent of the anti-vaccine movement – particularly in relation to the MMR vaccine in the early 200s. There were about 5000 cases in the UK in 2019.
- Mumps is a NOTIFIABLE DISEASE in the UK
- Another viral respiratory tract infection. Caused by the mumps virus.
- Most common in winter/spring
- Spread by droplet infection
- Not as infectious as measles
- Viral replication occurs in epithelial cells of the respiratory tract, before the virus gets into the parotid glands, and then spreads to other tissues.
- After previous infection, immunity is lifelong in 98% of cases
- Intrauterine infection can occur in pregnancy
Clinical features
- Nonsepcific malaise, headaches, myalgia, loss of appetite (anorexia)
- Painful swelling of the parotids (Parotitis)
- Often unilateral initially, becoming bilateral in 70% of cases
- May present as ear ache, or pain on eating and drinking
- The parotid duct may appear swollen and red on examination
- Fever – usually lasts 3-4 days
- Malaise
- Orchitis – can be present in boys. It is uncommon before puberty, and is usually unilateral. It can sometimes reduce sperm count, but infertility is extremely rare.
- Symptoms are generally less severe in young children, and worse in older children and adults
- The scrotum may be so swollen that the testes are not palpable
- Meninigitis
- Affects about 15% of patients
- Usually in cases without parotitis
- Usually mild and self limiting
- Encephalitis is a very rare but serious complication
Investigations
- Raised plasma amylase – due to pancreatic involvement. May also be associated abdominal pain.
- Oral fluid sampling – for confirmation of infection for public health
- In patients without parotitis then serum antibodies can be used to confirm infection
- Ultrasound scan – of the scrotum may be performed to help differentiate mumps orchitis from other causes – such as testicular torsion
Complications
- Hearing loss – relatively common, but usually self- limiting – typically presents several days after the clinical features have resolved
- Temporary hearing loss affects about 4% of patients
- Long term hearing loss affects about 1 in 20 000 patients
- Meningitis –a CSF picture compatible with meningitis is seen in about 50% of cases. However:
- Only 10% of cases have meningeal symptoms.
- Encephalitis – seen in 1 in 5000
- 1 in 1000 cases of mumps meningitis will develop mumps encephalitis
- 1.5% of these cases are fatal
- Orchitis – can cause infertility
- Pancreatitis
- Increased risk of miscarriage if contracted in the first trimester
- Mumps is not teratogenic
Treatment
References
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
- Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy