Measles

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 virus can remain transmissible for up to 2 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.⁵

• Infection traditionally has occurred within 3 and 6 years of age on starting education. However, transmission is uncommon in vaccinated school age children but younger children and susceptible adults are at risk.
• Disease mainly occurs in winter and spring with an outbreak every other year.
• 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.⁶ There has also been the first measles related death since 1992, in 2006. Poor uptake of MMR followed controversy surrounding the vaccination and an unproven link with autism.
• Other European countries with endemic measles include Romania, Germany, Switzerland and Italy. Between 2006-7, there were 12,132 confirmed cases of measles across Europe.⁷ Most were in unvaccinated or incompletely vaccinated children but almost a fifth were aged 20 years or older. Seven measles-related deaths were recorded over the same time period. This makes WHO's target for elimination of measles in the European region by 2010 seem doubtful.⁸
• In the US measles has been eradicated since 2002.

• Prodrome:
  • Lasts 2-4 days with fever, runny nose, mild conjunctivitis and diarrhoea.
  • Koplik spots are pathognomic and appear on the buccal mucosa opposite the second molar teeth as small, red spots each with a bluish-white speck (sometimes compared to a grain of rice) in the centre.⁹ 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):
  • First seen on forehead and neck and spreads, involves trunk and finally limbs over 3-4 days. It may become confluent in some areas.
  • 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 high fever (may be >40°C), non-productive cough, patient clearly ill.
• Also, swelling around eyes and photophobia.

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

• Salivary swab or serum sample for measles specific IgM taken within 6 weeks of onset.
• RNA detection in salivary swabs or other samples.
• Additional tests include buccal scrapings stained with Leishman's and examined under microscope for giant cells and immunofluorescence of an NPA (nasopharyngeal aspirate) sample.

• Rubella
• Parvovirus B19
• Enterovirus
• Scarlet fever
• Human herpes virus 7
• Kawasaki's disease
• Meningococcaemia
• Toxic Shock Syndrome
• Dengue fever
• HIV
• Secondary syphilis
• Drug eruptions

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

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% cases producing serious respiratory difficulties and accounts for 56-86% deaths. Infecting organism is usually Staph. aureus or secondary viral infection with Herpes simplex or adenovirus. Lobar pneumonia can occur and is caused by Strep. pneumoniae. Other secondary bacterial infections include cervical adenitis and otitis media. Lobar pneumonia should be treated with benzylpenicillin and bronchopneumonia with gentamicin, cloxacillin or co-trimoxazole.
• Giant cell pneumonitis in immunocompromised patients presents 2-3 weeks following measles infection with worsening breathing.

Neurological

Measles is associated with 3 different encephalitic diseases.

• Acute demyelinating encephalitis - occurs in 1-2/1000 cases of infection. Occurs within 2 weeks of the rash appearing usually with seizures often accompanied by fever, irritability, headache and changing consciousness that may progress to coma. Believed to be a neuroallergic process. Carries a 10-15% mortality rate with 25% children with permanent brain damage. Treatment is supportive with no clear benefit from dexamethasone.
• Subacute sclerosing panencephalitis - occurs in 0.1-1.4/million children infected. Commoner 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 extrapyramidal and pyramidal disease and finally decerebrate rigidity and death. Condition is untreatable.
• Measles inclusion body encephalitis - occurs in the immunocompromised 1-7 months following exposure and is progressive over months. It is largely fatal and of the approximately 15% survivors, all will have neurological sequelae.

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 may have frank vitamin A deficiency precipitated by measles. This usually manifests itself as xerophthalmia and is an important cause of blindness worldwide. 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 measles infection 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 world-wide.

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.

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% cases.
• Worldwide measles is responsible for >1 million deaths often due to pneumonia as a secondary bacterial infection and is the leading cause of vaccine preventable death.
• Complication and mortality rates are highest in infancy and lowest in 1-9 year olds, before rising again into adulthood.

Vaccination^12,13

• Currently use live strains attenuated by culture in chick fibroblasts.
• In developed world given at 14-16 months after maternal antibody that neutralizes the virus has disappeared.
• In developing world WHO recommends vaccination at 9 months when it has been shown to produce a significant reduction in all all-cause mortality greater than would be expected from merely preventing measles.¹²

Indications

• In UK given as part of MMR vaccination at around 13 months as seroconversion at this age is better than in younger children. A pre-school booster is required. Note that in developing countries where measles mortality is high, measles vaccine is given between 6 and 9 months but vaccine failure is more common.
• Older children and adults thought to be susceptible should receive 1 or 2 doses as required. Ideally the second dose should be given after 3 months but where protection is urgently needed, the second can be given a month following the first.
• Currently (2008-9), there is a MMR catch-up programme running in England and Wales to try to limit the risk of an epidemic outbreak. Target groups in order of priority are:²
  • Those aged 13 months to 18 years who have not received any MMR vaccine.
  • Partially immunised children aged 3 years 7 months (in September 2008) to 11 years.
  • Partially immunised children aged 12 to 18 years (school years 8 to 13).
  • Partially immunised individuals over 18 years leaving school to go to higher education or other further education establishments.
• HIV positive individuals should also receive MMR provided they are not too severely immunocompromised.

Contraindications

• Pregnant women
• Immunocompromised individuals
• Confirmed prior anaphylactic reaction to any of the viral vaccine components or to neomycin or gelatin

Post-exposure prophylaxis

• MMR vaccination may be effective if given to susceptibles (over 9 months old) if given 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 those aged less than 9 months.