Transmission

Measles is an acute infection caused by a single-stranded RNA Morbillivirus from the paramyxovirus family. It is highly contagious. Transmission is airborne via respiratory droplets. These spread to surfaces and the virus can remain transmissible for up to two hours, removing the need for direct person-to-person contact.

The infection has an average incubation period of 14 days (range 6-19 days) and infectivity lasts from 2-4 days prior to 2-5 days following the onset of the rash.³

Epidemiology

The epidemiology of measles is affected by uptake of vaccination. With extra efforts being made to improve the efficacy of vaccination programmes and a recovery of uptake after vaccine scares, it is apparent that the rates of confirmed measles in 2010 show a decline which it is hoped will be sustained.

It is important to consider the risk of transmission and vaccination history when travelling to countries which have outbreaks of measles.

• Infection traditionally has occurred within 3 and 6 years of age on starting education. Transmission is uncommon in vaccinated children of school age; however, younger children and susceptible adults are at risk.
• In England and Wales, there were 1,217 cases of confirmed measles between January and the end of November 2008 - the highest for 13 years.⁴ There has also been the first measles-related death since 1992, in 2006. This coincided with poor uptake of measles, mumps and rubella (MMR) vaccine and the controversy surrounding the vaccination and an unproven link with autism. See separate article Measles, Mumps and Rubella (MMR) Vaccination.
• Just 47 cases of measles were confirmed in the last quarter of 2010. This compares with 199 cases in the previous quarter. The total number of laboratory-confirmed cases in England and Wales for 2010 was 374, much reduced from the 1,144 cases confirmed in 2009.⁵
• Other European countries with endemic measles include Romania, Germany, Switzerland and Italy. Between 2006-2007, there were 12,132 confirmed cases of measles across Europe. Most were in unvaccinated or incompletely vaccinated children; however, almost a fifth were aged 20 years or older. Seven measles-related deaths were recorded over the same time period.
  In April 2011, 33 European countries have reported 6,500 cases of measles. Genotyping has confirmed transmission of measles between several countries in Europe and the Americas. France has reported 4,937 cases between January and March 2011 which compares with 5,090 cases in the whole of 2010.⁶
• In the USA, measles has been virtually eradicated since 2002. There were only 140 cases in the USA in 2008.⁷

Presentation

• Prodrome:
  • This lasts 2-4 days with fever, runny nose, mild conjunctivitis and diarrhoea.
  • Koplik's spots are pathognomonic and appear on the buccal mucosa - opposite the second molar teeth - as small, red spots, each with a bluish-white speck (sometimes compared with a grain of rice) in the centre.⁸ They occur in 60-70% of patients during the prodrome and for up to 2-3 days before the onset of the rash.
• Rash (morbilliform = measles-like):
  • This is first seen on the forehead and neck, and spreads, involving the trunk and finally the limbs over 3-4 days. It may become confluent in some areas.
  • The rash then fades after 3-4 days in the order of its appearance.
  • It leaves behind a brownish discoloration, sometimes accompanied by fine desquamation.
• Often, there is high fever (may be >40°C), a nonproductive cough, and the patient is clearly ill.
• Also, swelling around eyes and photophobia.

Clinical recovery in uncomplicated measles tends to occur soon after the appearance of the rash.

Investigations

• Salivary swab or serum sample for measles-specific immunoglobulin M (IgM) taken within six weeks of onset.
• RNA detection in salivary swabs or other samples.
• Additional tests include buccal scrapings stained with Leishman's stain and examined under microscope for giant cells and immunofluorescence of a nasopharyngeal aspirate (NPA) sample.

Differential diagnosis

• Rubella
• Parvovirus B19
• Enterovirus
• Scarlet fever
• Human herpes virus 7
• Kawasaki's disease
• Meningococcaemia
• Toxic shock syndrome
• Dengue fever
• Human immunodeficiency virus (HIV)
• Secondary syphilis
• Drug eruptions

Management

There can be significant public health implications and these need careful consideration as a matter of urgency alongside management of the affected individual.

Individual management

• Uncomplicated measles is usually self-limiting and treatment is mainly symptomatic, with paracetamol or ibuprofen and with plenty of fluids. Patients should remain at home to limit disease spread.
• Monitor patients carefully for signs of complications and consider hospitalisation if these appear.

Public health management

• Early detection of outbreaks can prompt vaccination campaigns to limit spread where appropriate.
• Vulnerable contacts (infants, pregnant women and immunocompromised individuals) should be identified for post-exposure prophylaxis where appropriate.
• Any susceptible healthcare workers need urgent assessment because they can be a source of transmission.
• Even healthy contacts (including unimmunised children and adults) may benefit from post-exposure vaccination.¹

Complications

Rates of complications vary by age, geographical region and outbreak. They increase where there is co-existent immunodeficiency, malnutrition, vitamin A deficiency and high exposure levels due to overcrowding.

Respiratory

• Bronchopneumonia occurs in up to 5% of cases, producing serious respiratory difficulties, and it accounts for 56-86% of deaths.The infecting organism is usually Staphylococcus aureus or secondary viral infection with herpes simplex or adenovirus. Lobar pneumonia can occur and is caused by Streptococcus pneumoniae. Other secondary bacterial infections include cervical adenitis and otitis media. Lobar pneumonia should be treated with benzylpenicillin and bronchopneumonia with gentamicin, flucloxacillin or co-trimoxazole.¹⁰
• Giant cell pneumonitis in immunocompromised patients presents 2-3 weeks following infection with measles, with worsening breathing.

Neurological

Measles is associated with three different encephalitic diseases:

• Acute demyelinating encephalitis - this occurs in 1/1,000 cases of infection.¹⁰ It occurs within two weeks of the rash appearing, usually with seizures often accompanied by fever, irritability, headache and changing consciousness that may progress to coma. It is believed to be a neuro-allergic process. It carries a 10-15% mortality rate and 25% of children have permanent brain damage. Treatment is supportive with no clear benefit from dexamethasone.
• Subacute sclerosing panencephalitis - this occurs in 1/25,000 of children infected.¹⁰ It is more common in boys and, where the initial infection occurs before the age of 2, onset is usually 5-10 years after apparently normal measles, with disturbance in intellect and personality, behavioural disorders and worsening school work. This is followed by seizures, signs of extra-pyramidal and pyramidal disease and, finally, decerebrate rigidity and death. The condition is untreatable.
• Measles inclusion body encephalitis - this occurs in the immunocompromised 1-7 months following exposure and is progressive over months. It is largely fatal and, of the approximate 15% of survivors, all will have neurological sequelae.^10,11

Gastrointestinal

Measles is commonly accompanied by diarrhoea due to secondary bacterial or protozoal infections. This is particularly significant in malnourished individuals. Clinical hepatitis and hypocalcaemia may also occur, more usually in adults.

Vitamin A deficiency and blindness

Those with borderline vitamin A deficiency are at greater risk of death and blindness from measles. Vitamin A deficiency manifests itself as xerophthalmia and is an important cause of blindness worldwide. The WHO recommends high-dose vitamin A for all children with measles in countries where the case fatality rate is greater than 1%.

Immunodeficiency

Infants and adults show delayed recovery from the lymphopenia that infection with measles causes. Even after lymphocyte counts have normalised, immunodeficiency persists for many weeks and this is thought to be a major contributor to the high all-cause mortality following acute measles worldwide.

Obstetric

Like many infections, measles can be more severe in pregnancy, as a potentially fatal pneumonitis may follow. Measles is also associated with increased risk of miscarriage, prematurity, low birthweight but not congenital malformation.

Prognosis

Disease severity varies from mild (usually in the well-fed child) to severe (usually in the malnourished or immunosuppressed patient). However, severe measles can occasionally present in a previously healthy child and particularly in young adults who have not been vaccinated or exposed to the virus naturally.

• In the West, mortality is <0.05% of cases.
• Worldwide, measles is the leading cause of vaccine-preventable death.¹²
• Complication and mortality rates are highest in infancy and lowest in 1-9 year-olds, before rising again into adulthood.

Prevention

See separate Measles, Mumps and Rubella (MMR) Vaccination article.

Post-exposure prophylaxis

• MMR vaccination may be effective if given to susceptibles (over 9 months old) within 72 hours of exposure.
• Human normal immunoglobulin should be considered within 5 days of exposure for severely immunocompromised individuals, pregnant women negative for measles IgG, and for those aged less than 9 months.

Document references

1. Guidelines on Measles, Health Protection Agency (2009)
2. Regional Committee for Europe September 2010, World Health Organization (WHO); Renewed commitment to measles and rubella elimination and prevention of congenital rubella syndrome in the WHO European Region by 2015
3. de Swart RL; The pathogenesis of measles revisited. Pediatr Infect Dis J. 2008 Oct;27(10 Suppl):S84-8. [abstract]
4. Kmietowicz Z; Cases of measles in England and Wales are highest for 13 years. BMJ. 2008 Dec 1;337:a2820. doi: 10.1136/bmj.a2820.
5. Health Protection Report, Immunisation, Health Protection Agency (2011)
6. Global Alert and Response (GAR) report, World Health Organization (WHO)
7. Faststats on Measles, Centers for Disease Control and Prevention (CDC)
8. Koplik's Spot, University of Leeds Dentistry department website: Viral infections; Image of typical Koplik's spot
9. Recommended surveillance standard of measles, World Health Organization (WHO)
10. Asaria P, MacMahon E; Measles in the United Kingdom: can we eradicate it by 2010? BMJ. 2006 Oct 28;333(7574):890-5.
11. Measles, Health Protection Agency; General information and up-to-date current statistics
12. Measles, World Health Organization (WHO); Worldwide epidemiology and targets

Internet and further reading

• Measles, DermIS (Dermatology Information System)
• No authors listed; Progress in global measles control and mortality reduction, 2000-2007. MMWR Morb Mortal Wkly Rep. 2008 Dec 5;57(48):1303-6.

Acknowledgements