Measles: what to be aware of during an outbreak

New Zealand is currently in the midst of a measles outbreak, which began in December, 2013. As of 15 August 2014, 281 cases of measles have been reported in New Zealand, mostly linked to international travel (113 cases in Auckland and 125 in Waikato).¹

Measles (“English measles”, rubeola) is a highly contagious viral disease that is characterised by rash and fever and is associated with a number of serious complications. The best protection against measles is immunisation with the combined measles, mumps and rubella (MMR) vaccine. The MMR vaccine was added to the National Immunisation Schedule in January 1990, and is currently recommended for children at age 15 months with a second dose at age four years.² MMR replaced the separate measles and rubella vaccines that had previously been on the schedule since 1969 and 1970, respectively (for further details of the vaccination timeline see: “MMR vaccination”).²

To protect against measles, all people born on or after 1 January 1969 should receive two doses of a measles-containing vaccine.² Anyone who has only received a single measles vaccine prior to the introduction of the combined MMR vaccine should receive two doses of MMR to offer best protection. There is no safety concern in regards to giving an extra measles vaccine. People born prior to 1969 are considered to be immune to measles as it is presumed they would have been exposed to wild-type measles prior to the introduction of the measles vaccine.²

According to the World Health Organisation (WHO), 95% of the world’s population born after the measles vaccination was introduced, need to be fully vaccinated against measles in order for the disease to be eliminated.³ Between 1980 – 2012, 81% of children aged two years in New Zealand received a measles-containing vaccine.³ In 2006 and 2007, 92 – 93% of children received the first dose of MMR, but only 89% received the second MMR dose.³ These immunisation rates for MMR are not high enough to prevent outbreaks of measles. However, the most recent statistics for 2008 – 2011 are encouraging, with national coverage rates of 93% – 94% for the first dose of MMR in children aged two years.³

Who can contract measles?

Both adults and children can contract measles but the incidence rate decreases with increasing age. Children aged less than one year are still the most likely age group to be infected with measles as they have not yet received the MMR vaccine. However, there was an increase in the infection rates in adolescents aged 10 – 14 years during the 2009 and 2011 outbreaks.³ This was likely due to changes in the MMR vaccination schedule and less than optimal vaccination rates for the birth cohort born between 1990 and 2000 (see: “MMR vaccination”). Measles infection results in lifelong immunity and people can only contract the disease once, but occasionally people who have received MMR can still contract measles (due to inadequate immune response or inadequate vaccination). Of the 68 cases of measles reported in 2012, 40 were in unvaccinated people (including 20 cases in children aged less than 15 months), 10 were in people who had received one dose of MMR and seven were in people who had received two doses of MMR. Vaccination status was unknown in the remaining 11 people.²

People most at risk of contracting measles include those who have not been vaccinated with MMR, those who are returning from international travel (due to higher risk of exposure in measles-endemic countries) and those born overseas in countries where appropriate vaccination is less likely.

What is measles?

Measles is caused by a paramyxovirus and transmission is by direct person-to-person contact via oropharyngeal and nasopharyngeal droplets, and less commonly via airborne spread or contact with infected surfaces, e.g. door handles and eating utensils, as the virus can survive on these surfaces for several hours. Measles is one of the most highly communicable of all infectious diseases. There is an incubation period of approximately 10 – 14 days after exposure before symptoms appear.¹

The signs and symptoms are highly characteristic in most people and tend to appear in three stages:⁷

Prodromal stage, lasting three to four days, where symptoms can include fever of greater than 38°C, malaise, anorexia, diarrhoea, Koplik spots (tiny white spots like grains of salt on the buccal mucosa), the “3Cs” of cough, coryza (rhinitis) and conjunctivitis.

Exanthema (rash) stage, lasting four to five days, and characterised by a blotchy, bright red maculopapular rash that is generally not itchy. This rash typically starts behind the ears and then spreads to the face and neck and then the rest of the body.

Convalescent stage where the rash fades leaving a temporary brownish stain on the skin.

Differential diagnoses for measles include other causes of rash, fever and conjunctivitis, e.g. drug sensitivities, roseola, enterovirus, adenovirus and infectious mononucleosis (EBV) infections, scarlet fever, Kawasaki disease and rubella.⁸

Laboratory testing and notification

Confirming clinically suspected cases of measles with laboratory testing is recommended. The virus is more likely to be present within the first week of onset of rash, so ideally sampling should occur within this time period.⁹ Measles is a notifiable disease and the Medical Officer of Health should be notified as soon as measles is suspected and prior to laboratory confirmation.

A nasopharyngeal swab in a vial of universal transport medium is the preferred method of testing.⁹ However, if unavailable, throat swabs may be used in young children. A blood sample (for serology) can also be used as long as the rash has been present for at least three days.⁹ Local protocols on testing vary, i.e. whether testing is done locally or sent to another laboratory – clinicians should check with their local laboratory to see where testing is performed. Once measles has been isolated, samples are sent to the New Zealand National Measles Laboratory (at Canterbury Health Laboratories).⁹

N.B. Swabs are best taken in the general practice (or initial site of contact with the patient), so other patients at laboratory collection centres are not exposed to the virus.

For further information, see: www.measles.co.nz/specimen-guidelines

Prevention of transmission

People with measles are infectious for five days before and after the rash appears.¹ This can make prevention and control measures difficult to implement as people are infectious well before symptoms become apparent. However, some measures can be implemented in health clinics during outbreaks and when dealing with a patient with suspected measles. This can include having suitable triage and isolation areas for patients, allowing only immune staff to have contact with the patient, and having hand gels and surgical masks at reception areas and at practice entrances/exits. Children should be kept away from day care or school for at least five days after the rash appears.⁷ Transmission between family/household members is common and people with suspected or confirmed measles should avoid contact with non-immune infants and pregnant women.

In the event of a measles outbreak, The Immunisation Advisory Centre advises that non-immunised children (who have not had measles and whose parents do not want them to receive MMR) who have contact with people with measles should not attend school or early childhood services (or be in public places) until notified. This may be for a period of 14 days (incubation time).

MMR and immunoglobulins as prophylaxis for measles

There are only a few management options available that may help prevent infection after people have potentially been exposed to measles. These include either active (MMR) or passive (human immunoglobulin) immunisation.

MMR: During outbreaks, or other circumstances when protection against measles is urgently required, MMR can be given to unvaccinated people, who are not immunocompromised, within 72 hours of exposure and this may prevent infection.⁵ If measles infections are being reported in very young infants, MMR can given to children aged six to 12 months, i.e. infants are fast tracked for vaccination before the recommended age of 15 months.² However, as the immune response may not be as effective, the child will still require a further two doses of MMR at age 15 months and four years.²

Human normal immunoglobulin (HNIG): This is a preparation of concentrated antibodies (immunoglobulins) that are not specific to a particular infection, but can boost immunity in people who are immunocompromised. An Infectious Diseases Specialist or Paediatrician may recommend intramuscular (IM) administration of HNIG in the following scenarios:⁴

• In people with contraindications to MMR
• In immunocompromised children and adults
• In pregnant women
• In children aged less than 15 months who present more than 72 hours after exposure to measles
• In people who present more than 72 hours after exposure and have no history of measles OR have not received MMR

HNIG prophylaxis should be given as soon as possible after exposure to measles, but can be administered for up to six days. It should not be administered within three weeks of a live virus vaccine and live virus vaccines should not be given for 11 months after a patient has received HNIG.²

For further information on HNIG see: www.nzblood.co.nz/assets/Transfusion-Medicine/PDFs/POST-EXPOSURE-PROPHYLAXIS-FOR-MEASLES-111G001.pdf

Intravenous (IV) Immunoglobulin (Intragram P): is a similar preparation as HNIG but is administered via the IV and not the IM route. Intragram P can be considered in immunocompromised people who have had contact with a person with confirmed measles, people who require large doses of immunoglobulin prophylaxis, and people with a reduced muscle bulk for whom IM administration would be difficult.²

Treatment of measles

There are no specific antiviral treatments for measles and patients usually improve within seven to ten days without treatment. However, patients/parents can be advised about some measures to help control the symptoms. These can include:

• Using analgesia, e.g. paracetamol or ibuprofen, to reduce pain and discomfort
• Ensuring adequate fluid intake to avoid dehydration, especially if febrile
• Treating sore eyes. This can include wiping the crustiness from the eyelids and lashes using cotton wool and water (use a separate piece of cotton wool for each eye) and avoiding bright light

Complications of measles and follow up

Complications from measles are common and up to 30% of people experience at least one complication.⁵ The most common complications (with approximate rates) are otitis media (7 – 9%), pneumonia (6%) and diarrhoea (8%).⁵ The risks of complications are highest in children aged less than five years, in adults aged over 20 years and in people who have chronic co-morbidities (especially those who are immunocompromised).⁵

Approximately one in 1000 people who contract measles will die; pneumonia accounts for approximately two-thirds of these deaths.⁵ Death rates are much higher than this in less developed countries. Some of the more serious complications of measles include acute encephalitis (approximately 0.1% of people) and subacute sclerosing panencephalitis, a rare degenerative central nervous system disease, which is always fatal, and occurs in approximately one in 100 000 people.⁵ Contracting measles during pregnancy can increase the risk of premature labour and miscarriage.⁵

Patients should be informed of the possible complications of measles and advised to contact a health professional at any time when they are concerned about their symptoms, if their condition worsens, or if their symptoms are not resolving.