Measles

Part of the Communicable Disease Control Manual

Chapter last reviewed and updated in November 2022. A description of changes can be found at Updates to the Communicable Disease Control Manual.

Contents


Epidemiology in New Zealand

In 2017, Aotearoa New Zealand was verified by the World Health Organization as having eliminated endemic measles. It has maintained elimination since then. This means that there has not been sustained transmission of measles for longer than a year in New Zealand since 2014. However, measles is often imported into New Zealand following international travel.

New Zealand has continued to experience outbreaks of measles in recent decades. This is due to historically low immunisation rates and therefore insufficient levels of immunity across the population to prevent community transmission. Prevention of measles outbreaks relies on improving coverage with measles-mumps-rubella (MMR) vaccination.

More detailed epidemiological information is available on the Institute of Environmental Science and Research (ESR) surveillance website.

Case definition

Clinical description

An illness characterised by all of the following:

  1. cough and/or coryza and/or conjunctivitis and/or Koplik’s spots present at the time of rash onset
  2. fever (at least 38ºC if measured) present at the time of rash onset
  3. generalised maculopapular rash, starting on the head and neck then spreading down and out and fading

Laboratory test for diagnosis[1]

Nucleic acid amplification tests (NAAT), eg, PCR, are preferred for diagnosis. Nasopharyngeal or oropharyngeal samples have the highest yield particularly in the seven days after the onset of rash. Urine testing can be useful for those presenting more than three weeks after onset of rash. Submitting both a throat or nasopharyngeal swab and a urine sample provides the best yield if sampling is delayed. 

Definitive laboratory evidence for a confirmed case is:

  • A positive NAAT of a non-vaccine strain

Suggestive laboratory evidence is: 

  • IgG seroconversion between paired sera tested in parallel  
  • IgM detection in an unvaccinated person  

The use of serology in the investigation of a suspected measles case is only recommended in cases where NAAT is not possible AND if requested by a medical officer of health after discussion with a clinical microbiologist. Any positive IgM result should be discussed with a clinical microbiologist.

Genotyping information is useful for epidemiology and outbreak investigation. Genotyping via sequencing can be performed on measles-positive NAAT samples at the National Measles and Rubella Reference Laboratory (NMRL) at Canterbury Health Laboratories (CHL), Christchurch. Genotyping should be performed on all:

  • New importations
  • Index cases and the first 5-10 cases of an outbreak/cluster. If outbreaks continue, then additional samples should be genotyped on a monthly basis
  • Sporadic cases that are not epidemiologically linked to other genotyped cases or clusters, and
  • All samples requested by the medical officer of health investigating the outbreak.

Samples from patients with recent measles vaccination history can also be tested for the presence of the measles vaccine strain at CHL, SCL Dunedin and LabPlus in Auckland via a vaccine-strain-specific PCR assay.

All requests for NAAT for measles and samples referred for genotyping or testing for the presence of the measles vaccine strain should have recent vaccination status included on the request form.

Sample requirements:

  • For genotyping via sequencing and vaccine-strain-specific PCR a minimum of 1 mL of primary patient sample (ideally nasopharyngeal swab sample in universal transport medium) should be sent to the respective laboratory
  • In addition, 1 mL of all positive samples should be sent to the NMRL at CHL if possible
  • If this is not possible during an outbreak, with high sample numbers, then at least 10 positive samples per week (and all those samples that require genotyping) should be forwarded to the NMRL at CHL.

Note: laboratory testing is not always required for contacts of known cases to be classified as confirmed cases. 

Interpreting serology 

Serology is most useful for detecting IgG in those who have an unclear vaccination history, although commercial assays do not detect all vaccine-induced immunity. There are limited circumstances where IgG testing may be appropriate to test exposed contacts to determine if they are immune, such as: 

  • Immunocompromised people or pregnant women for whom normal human immunoglobulin (NHIG) may be recommended if they are known to be susceptible
  • Healthcare workers for whom it is too late for post-exposure prophylaxis to be effective. 
  • People who need to be excluded from critical duties unless they have demonstrable immunity to measles
  • Seeking confirmation of immune status due to unknown vaccination status or partially vaccinated individuals (to support decisions regarding restriction requirements or necessity for a booster vaccination). 

Limitations

IgM serology is often unreliable, particularly in previously vaccinated people. Recent vaccination may result in an IgM response, and previously vaccinated but infected persons may not develop an IgM response. IgM serology confirmed by the reference laboratory may occasionally help in late presentations and should be interpreted in discussion with a clinical microbiologist.  

After measles vaccination, measles IgM is produced as part of the seroconversion and can be detected for 1–2 months. Serologically diagnosed cases who have received a measles-containing vaccine 8 days to 6 weeks before testing should not be classified as confirmed measles cases unless they are also linked epidemiologically to another confirmed case before vaccination.  

Measles IgG detected without IgM within 1–2 days of a rash strongly suggests prior immunity and that the rash is more likely due to causes other than measles. 

Case classification

  • Under investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed.
  • Probable: A clinically compatible illness where there is a high index of suspicion* of disease, and either laboratory suggestive evidence** or laboratory confirmatory testing is inconclusive or cannot be performed.
  • Confirmed: A clinically compatible illness that is laboratory confirmed or epidemiologically linked to a confirmed case.
  • Not a case: A case that has been investigated and subsequently found not to meet the case definition.

* A high index of suspicion is if someone has a clinically compatible illness, is susceptible to measles (not immune/immunised) and has been in an area with known measles cases (either in Aotearoa New Zealand or overseas) during the incubation period OR when there is an epidemiological link to a probable case.

** See ‘Laboratory test for diagnosis’ above

Spread of infection

Incubation period

About 10 days, but may be 7–18 days, from exposure to onset of fever, and about 14 days, but may be 7–21 days, from exposure to the onset of rash. The incubation period may be longer in those given immunoglobulin after exposure.

Mode of transmission

Airborne spread or by direct contact with nasal or throat secretions of cases. The measles virus has a short survival time (less than 2 hours) and is rapidly inactivated by heat, sunlight and pH extremes. Both ventilation and masking are effective at reducing (but not necessarily preventing) transmission of airborne diseases.

Infectious period

For public health purposes, the case is considered infectious from 4 days before appearance of rash to 4 full days after onset of rash (counting the day of rash onset as day 0), ie, this is a total of 9 days.

Note: days are measured in 24 hours.

Notification procedure

Attending health practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification from health practitioners should not await confirmation.

Management of case

Investigation

Wherever possible, all relevant clinical and demographic information on the suspected case should be collected within one day.

Obtain a history of vaccination, immunodeficiency, contact with a probable or confirmed case and travel.

In consultation with the attending health practitioner, obtain laboratory confirmation where possible and necessary. Testing may not be necessary or appropriate for cases with an epidemiological link to a confirmed case in outbreak situations.

Restriction

Isolate (ie, stay home unless seeking health care) for at least four days after the appearance of the rash. If seeking health care call ahead to inform that they are infectious with measles.

In health care facilities, airborne precautions should be taken until four days after the appearance of the rash.

Treatment (supportive)

Vitamin A treatment can reduce the risk of fatality and eye complications and should be considered particularly in cases of hospitalised children, and in cases with severe or complicated measles, immunodeficiency, malabsorption, malnutrition or documented vitamin A deficiency.

Counselling

Advise the case and their caregivers of the nature of the infection and its mode of transmission. If other vaccinations are incomplete, recommend the case catches up once they are through the acute illness.

Active case finding

Public health services should alert doctors and laboratories in areas where the case may have acquired the infection or was infectious and should ask these doctors and laboratories to notify all cases to the public health service promptly. Part of the reason for this is that early prophylaxis given to susceptible contacts (see below) can reduce the risk of developing disease. Consider a media alert to assist in finding cases.

Management of contacts

Definitions

Contact

Any person who has been in a confined space with an infectious case or has spent time in that space within one hour after it has been vacated by the case.

Confined settings may include early childhood services, classrooms, households, transportation, waiting rooms, consultations rooms, indoor occupational or social settings. Some judgement may be required by the local medical officer of health, noting that measles is highly infectious, and this should be taken into account when determining contacts and public health action. However, if appropriate control measures (eg, mask wearing, ventilation, and other infection prevention and control measures) have been in place, a medical officer of health may use their discretion in determining whether a person is a contact or not.

Susceptible contact

  • Any contact who does not have acceptable presumptive evidence of immunity (see below).

Acceptable presumptive evidence of immunity

  • Date of birth before 1 January 1969[2] (they are presumed to be immune following exposure to the wild virus).
  • Documentation of vaccination.
    • For children aged 12 months to under 15 months: documentation of at least one dose of measles-containing vaccine after their first birthday.
    • For individuals aged 15 months and older: documentation of two doses of measles-containing vaccine, given at least one month apart and given after their first birthday. This can include the contact’s second measles-containing vaccine after exposure to an infectious case as long as it has been given within 72 hours of initial exposure.
  • Documentation to confirm immunity, eg, serology.
  • Documentation of previous infection, eg medical records.

Prophylaxis

For susceptible contacts, consider the use of MMR vaccine, human normal immunoglobulin (HNIG) or intravenous immunoglobulin (IVIG) as described in the Immunisation Handbook. Appendix 6 of the Immunisation Handbook outlines considerations around passive immunisation with immunoglobulin. There is some evidence that a dose of MMR vaccine, when given to an unvaccinated or partially vaccinated person within 72 hours of first contact with an infectious case, may reduce the risk of developing disease.

If there is doubt about a contact’s immunity, give MMR vaccination as there are no undue effects from vaccinating an individual who is already immune.

Restriction

Susceptible contacts quarantine (ie, stay home unless seeking health care) from seven days after first exposure to an infectious case until 14 full days after last exposure to an infectious case. That is, if there has been a single exposure, quarantine is for seven days (from 7 until 14 days after exposure). However, if exposure has been for more than one day (potentially exposure to several cases with differing infectious periods), then quarantine will be for more than seven days.

However, partially vaccinated contacts (those with only one documented dose of MMR):

  • Will not be requested  to quarantine, but
  • Should be excluded from higher risk settings*, unless the setting is one where all others present have acceptable presumptive evidence of immunity, and
  • The contact will continue to be monitored for signs and symptoms consistent with measles for at least 14 days, and
  • A second MMR needs to be administered as soon as possible (but at least four weeks from the first dose).

* Higher risk settings include early childhood education centres, healthcare, and other settings where there may be high levels of contact and with susceptible people who may be more prone to developing severe disease if infected.

The medical officer of health should consider whether it is necessary to exclude children who are contacts from early childhood services using the Education (Early Childhood Centres) Regulations 1998.

Further information on post exposure MMR vaccination and quarantine/exclusion, including an algorithm, is available at Post-exposure MMR vaccination and exclusion.

Non-susceptible contacts (see ‘Acceptable presumptive evidence of immunity’ above) need no restriction.

Counselling

Advise all contacts to seek early medical attention if symptoms develop and take precautions so as not to infect others. It is important they telephone and alert the health provider before attending their medical centre to prevent the risk of spreading the virus in health care settings.

Other control measures

Health education

Stress the importance of two doses of measles vaccination for all children and encourage early childhood services to keep up-to-date immunisation records for all attending children.

Two doses of MMR vaccine are recommended for all children (without contraindications): the first at 12 months of age and the second at 15 months of age. Where dose/s have been delayed or missed, catch-up vaccination is recommended. 

Catch-up vaccination is recommended for anyone born from 1 January 1969 who has missed doses of measles vaccine (or who cannot show they are immune).

New Zealand residents are eligible for a free primary course (two doses of MMR vaccine).

Depending on circumstances, such as during an outbreak or prior to international travel, a second MMR dose may be given 1 month after the first dose. During a generalised community outbreak, an extra dose (dose 0) may be offered to infants 6–12 months of age, but as effectiveness cannot be guaranteed, all children still need two further doses when they are over 12 months of age. This is because the seroconversion rate is lower when MMR is administered to an infant under 12 months of age.

Infection control

Ensure that the attending health practitioner and laboratory collection rooms understand the importance of prompt isolation of a suspected case within their health care facility and the need to leave the consultation/examination room vacant for at least 1 hour after the suspected case has left it. Visits of cases and contacts (who may be entering the infectious period) to laboratory collection rooms should be planned ahead by telephone.

Ventilation and masking are effective at reducing transmission of airborne diseases.

Reporting

Ensure complete case information is entered into EpiSurv.

If an outbreak occurs, inform Te Whatu Ora National Public Health Service team and outbreak liaison staff at ESR, and complete the Outbreak Report Form.

References and further information

 


[1]    Culture is no longer performed in New Zealand but may be used overseas to diagnose someone who was infected in New Zealand and considered as a confirmed case from New Zealand.

[2]    Measles vaccine was introduced into New Zealand in 1969.

Back to top