Measles

Overview

Measles is an acute, highly communicable viral disease caused by the measles virus.

Disease epidemiology

Measles occurs worldwide, and despite the availability of a safe and effective vaccine, it remains a significant cause of mortality in young children. In countries that have implemented effective childhood vaccination programmes, the incidence of measles has dropped by up to 99%. However, there has been a recent global resurgence in measles cases due in part to vaccine hesitancy and falling coverage. Population immunity needs to be maintained at more than 95% to prevent outbreaks.

In Singapore, measles vaccination was made compulsory in 1985. Trivalent measles, mumps, rubella (MMR) vaccine was introduced in 1990. From 1992 to 1997, a spike in cases (due to a build-up of susceptible persons who were not vaccinated) resulted in “catch-up” immunisations from July to November 1997. A two-dose MMR regime was introduced in 1998.

Pathogen(s)

Measles virus.

Transmission

Measles primarily transmits through inhalation or direct deposition of infectious respiratory particles (IRPs) such as when an infected person coughs or sneezes. It can also spread via contact with contaminated surfaces such as when IRPs settle on surfaces or transfer through direct contact (e.g. handshake) before reaching the mouth, nose or eyes.

Incubation period: Typically 8 to 14 days; ranging from 7 to 21 days.

Infectious period: From 4 days before (from the onset of prodromal symptoms) and up to 4 days after onset of rash.

Clinical features

The illness usually starts with fever and the 3 C’s (cough, coryza and conjunctivitis). Koplik’s spots appear during the febrile phase. These are 1-2 mm diameter whitish-grey spots surrounded by erythematous rings at the buccal mucosa opposite the molar teeth. Typically, between the third to fifth day of illness, a maculopapular rash appears – first behind the ears, or over the eyelids, then spreading to the rest of the face and upper neck and then the rest of the body (centrifugal, top down). Fever usually peaks with the appearance of the rash and lasts for another 3-4 days. The rash darkens and fades after about 5 days, sometimes with desquamation. Individuals who are partially vaccinated/immune may present with a milder illness or atypical rash and clinical manifestations.

Complications of measles include diarrhoea, otitis media, pneumonia and encephalitis, and can result in permanent impairment (e.g. deafness, intellectual disability) and mortality. Case Fatality Rate of measles is <1% in developed countries and 3-5% in developing countries.

Differentials for measles rash include roseola infantum, rubella other viral exanthem (e.g. Echovirus, coxsackievirus, parvovirus B19), Kawasaki disease, and drug rash.

Risk factors

• Persons who are partially vaccinated or unvaccinated against measles

• Persons with weakened immune systems

• Persons travelling or living in areas with ongoing transmission or outbreaks

Diagnosis

Positive results for polymerase chain reaction, virus isolation, antigen immunofluorescence or serology (IgM or four-fold rise in antibody titre).

Treatment and management

There is no specific antiviral therapy for measles and treatment is supportive, focusing on symptomatic measures (e.g. antipyretics), prevention and treatment of complications. Those with complications require hospitalisation for further management. Antibiotics may be considered for treatment of secondary bacterial infections.

Vitamin A may be given to children with severe measles who are hospitalised and with risk factors for Vitamin A deficiency/who are malnourished.

Precaution, prevention, and control

Isolation measures

All cases in the healthcare setting should be isolated and managed under airborne precautions.

Contact management

Susceptible contacts should be offered post-exposure prophylaxis to reduce the risk of infection and complications. The MMR vaccine can be administered within 72 hours of exposure, if there are no contraindications. For those in whom the MMR vaccine is contraindicated (e.g., pregnant, immunocompromised, or young infants), immunoglobulin can be given within 6 days of exposure. At a later date, measles vaccine should be offered to those in whom the vaccine is not contraindicated for future protection.

Only healthcare workers with measles immunity should take care of patients.

All unvaccinated close contacts who are eligible for vaccination should receive the vaccine as soon as possible.

Vaccination

Vaccination remains the primary preventive measure against measles and is compulsory by Singapore law. As measles is a highly contagious disease, at least 90% to 95% of the population need to be vaccinated to maintain herd immunity. Proof of vaccination is required for admissions to preschools and primary schools. Catch-up vaccination is carried out for primary one students (6 to 7 years of age) who did not receive the second dose in their pre-school years.

The National Childhood Immunisation Schedule (NCIS) recommends that all children should receive 2 doses from age 12 months onwards, at least 4 weeks apart.

The National Adult Immunisation Schedule recommends that adults (18 years or older) who have not been vaccinated, or lack evidence of past infection or immunity should receive 2 doses (the first dose, and the second dose 4 weeks after the first dose).

Given the increase in measles cases globally, travellers are advised to be fully vaccinated against measles before travel. Those who are uncertain about their immunity status are recommended to seek medical assessment at least 4 to 6 weeks before travel to confirm measles immunity, or receive the MMR vaccine. For infants aged 6 to 11 months old who are travelling to countries with measles outbreaks or high measles incidence, they are advised to receive 1 dose of MMR vaccine at least 2 weeks before their travel to reduce the risk of infection during the trip.

Even if an infant has had 1 dose of MMR vaccine before 12 months of age, they should still follow the recommendations in NCIS and receive 2 additional doses at 12 months (first dose at least 4 weeks from the additional dose received before 12 months) and 15 months (second dose) for long term protection.

Notification

Measles is a legally notifiable disease in Singapore.

Who should notify:

• Medical practitioners

• Laboratories

When to notify:

• Medical practitioners – on clinical suspicion

• Laboratories – on laboratory confirmation

How to notify:

• Please refer to the Infectious Disease Notification for more information.

Notification timeline:

• As soon as possible. No later than 24 hours.

Resources

Please refer to the Weekly Infectious Diseases Bulletin for the number of measles cases in Singapore.

For more information on measles, please refer to the World Health Organization website.

For general travel advisory, please refer to Health Advice for Travellers.