Measles

Notification requirement for measles

Measles is an ‘urgent’ notifiable condition and must be notified by medical practitioners and pathology services immediately by telephone upon initial diagnosis (presumptive or confirmed). Pathology services must follow up with written notification within 5 days.

This is a Victorian statutory requirement.

Primary school and children’s services centres exclusion for measles

Exclusion for cases and contacts is as follows:

• Cases should be excluded for at least 4 days after rash onset.
• Immunised contacts do not need exclusion.
• Unimmunised contacts should be excluded until 14 days after the first day of appearance of rash in the last case. If unimmunised contacts are vaccinated within 72 hours of their first contact with the first case, or if they receive immunoglobulin within 144 hours of the contact, they may return to school.

Infectious agent of measles

Measles virus is a member of the genus Morbillivirus.

Identification of measles

Clinical features

Clinical features of measles include prodromal fever, a severe cough, conjunctivitis, and coryza in a moderately unwell child. Koplik spots may be seen on the buccal mucosa around 2 days prior to rash onset.

The most important clinical predictors are included in the clinical case definition for measles, which is an illness characterised by:

• generalised maculopapular rash, usually lasting 3 or more days, and
• fever (at least 38 °C if measured) present at the time of rash onset, and
• cough or coryza or conjunctivitis or Koplik spots.

The characteristic red, blotchy rash appears on the third to seventh day. It begins on the face before becoming generalised and generally lasts 4–7 days.

Complications can include otitis media, pneumonia and encephalitis. Subacute sclerosing panencephalitis (SSPE) develops very rarely as a late complication.

People who have been previously immunised may present with non-classical features, although this is uncommon.

Measles infection (confirmed virologically) may rarely occur without a rash.

Diagnosis

The diagnosis should be confirmed by demonstration of anti-measles IgM antibody, detection of measles RNA by polymerase chain reaction (PCR) techniques (if available) or by viral culture. The latter is particularly useful for epidemiological purposes.

Suspected cases should be bled at the time of clinical diagnosis. The detection of anti-measles IgM increases to 100 per cent for samples taken 4–14 days after rash onset. If testing is negative for anti-measles IgM on a sample collected 3 days or less after rash onset, it should be repeated 4–14 days after rash onset. If there is a high clinical suspicion of measles and the patient is presenting within 3 days of rash, then the department may advise taking throat or nose swabs for PCR in order to implement early public health measures at the time of confirmation. This should be discussed at the time of notification.

The diagnosis can also be confirmed by demonstration of a fourfold or greater change in measles antibody titre between acute- and convalescent-phase sera. The sera should be obtained at least 2 weeks apart, and the tests should preferably be conducted in parallel at the same laboratory.

Serodiagnosis is not possible between 8 days and 8 weeks after measles vaccination. Viral genotyping or establishing an epidemiological link to a confirmed case may help to confirm a suspected case.

Incubation period of measles virus

The incubation period is approximately 10 days, but varies from 7 to 18 days from exposure to the onset of fever. It is usually 14 days until the rash appears.

Public health significance and occurrence of measles

The use of measles vaccine in infant immunisation programs globally has led to a significant reduction in measles cases and deaths. In addition to providing direct protection to the vaccine recipient, immunisation against measles results in the indirect protection of unimmunised people (herd immunity) if high enough coverage is achieved. Measles vaccine has several major effects on measles epidemiology, including an increase of the mean age of infection and an increase in the time between epidemics.

Despite the availability of an effective measles vaccine for almost 40 years, the disease still causes a considerable burden in many countries. In 2008, there were 164,000 measles deaths globally. Higher measles vaccination coverage (at 85 per cent in 2010) led to a 78 per cent drop in measles deaths globally between 2000 and 2008. Reductions in measles mortality accounted for 23 per cent of the estimated global decline in all-cause child mortality from 1990 to 2008. Most deaths occur in developing countries, principally in Africa and Asia. Forty-three countries reported routine measles vaccine coverage below 80 per cent in 2010. Large measles outbreaks continue to occur, especially in areas of developing countries with low vaccine coverage and among children living in countries where there are unstable social conditions. These outbreaks frequently have high case-fatality rates.

In Australia, live attenuated measles vaccine was licensed in 1968 and included in childhood vaccination schedules in 1971. Even after the first national measles campaign in 1988, coverage remained too low (85 per cent) to achieve herd immunity. This allowed major measles outbreaks in many areas in 1993 and1994. In 1994, a second dose of measles–mumps–rubella (MMR) vaccine was introduced for all children aged 10–16 years. Although the incidence of measles declined, seroprevalence studies indicated that further measles outbreaks were likely.

In July 1998, a ‘catch-up’ campaign was conducted to give a dose of MMR vaccine to all primary school children before lowering the recommended age for the second dose of MMR vaccine to 4 years in 1999. After the measles control campaign, an estimated 96 per cent of children aged 5–12 years had received two doses of MMR vaccine.

Although the endemic spread of measles has now been interrupted in Australia, small outbreaks have continued to occur following importations of measles cases from overseas. Adults born after 1966 who have not been vaccinated are most at risk, along with the small numbers of unimmunised children.

Reservoir of measles virus

Humans.

Mode of transmission of measles virus

Measles transmission is airborne by respiratory droplet nuclei spread or by direct contact with infected nasal or throat secretions. The virus can persist in the environment for up to 2 hours and is highly transmissible even without close contact. Transmission has been reported to people whose only apparent source of infection was a room previously occupied by a patient with measles.

Period of communicability of measles

Cases are infectious from slightly before the beginning of the prodromal period, usually 5 days prior to rash onset. They continue to be infectious until 4 days after the onset of the rash.

Susceptibility and resistance to measles

Natural infection provides lifelong immunity. A history of prior measles infection should be confirmed serologically before vaccination is deferred, as most reports of clinical measles infection are subsequently tested as negative.

Vaccination at 12 months of age produces a protective antibody in approximately 95 per cent of recipients. The second and third doses of vaccine, recommended at 18 months and 4 years, increases protection to approximately 99 per cent of recipients.

Control measures for measles

Preventive measures

Live attenuated measles vaccine is recommended for all people born after 1966 unless specific contraindications to live vaccines exist.

The childhood immunisation schedule (as of June 2015) recommends MMR vaccine be given at 12 months, 18 months of age as quadrivalent MMRV vaccine (MMR plus varicella) and at 4 years of age. The 4-year-old dose ends in December 2015.

Older children and adults born after 1966 who are unimmunised and those with serological evidence of non-immunity should be given at least one dose of MMR and ideally a second dose of MMR 1 month later.

A dose of MMR should also be given postpartum for non-immune women, followed a month later with a repeat dose. Pregnancy should be avoided for 28 days after vaccination, although transmission to the foetus is considered extremely unlikely should pregnancy occur.

Unimmunised healthcare workers, including medical practice staff, born after 1966 are at high risk of measles infection. The measles vaccination status of all healthcare workers should be assessed before they commence work, and non-immune workers should be vaccinated with two doses of MMR vaccine.

Control of case

There is no specific treatment for measles. Treatment is supportive, with particular attention to the possible complications of measles, particularly pneumonia and encephalitis.

The case should be immediately put in respiratory isolation to minimise any possible ongoing transmission. If the case requires hospitalisation, they should be nursed in an isolation room, preferably with negative pressure ventilation, using respiratory and standard precautions.

Cases not requiring hospitalisation should be advised to stay at home until they are no longer infectious, usually the fifth day after rash onset. Children are excluded from school or childcare for at least 4 days after the onset of the rash.

The department actively investigates all suspected measles cases to confirm the diagnosis, to identify the source of infection, to identify other cases, and to identify and protect susceptible contacts in the community.

Control of contacts

The department will trace and manage susceptible community contacts of cases. Identifying and protecting susceptible contacts exposed in healthcare institutions, such as medical practices or emergency departments, is the responsibility of the individual institution.

Contacts include (in priority order for prophylaxis):

• all household members
• all people sleeping overnight in the same room as the case (for example, in a hospital, boarding school or military barracks)
• all children and adults in family day care, childcare, preschool, school or other educational settings who share a classroom with the case
• people who stayed in a waiting area at the same time as the case (for example, patients in a healthcare facility’s waiting room and any people accompanying those patients) and people who waited in the waiting area or who were seen in the same consultation room up to 30 minutes after the case left
• all work colleagues of the case who share the same work area
• others who attend or work in the same educational institution as the case, and may have spent time in the vicinity of the case, but do not share a classroom (for example, in a high school, college or lecture theatre block)
• passengers on an aeroplane who were seated in the same row or two rows in front of or behind a case.

For others who cannot be individually identified but who may have been present in the general area where the case was known to be (for example, in cinemas, shopping centres, aircraft and restaurants) consideration should be given to the need to provide notices or media messages informing them of their possible exposure.

A person considered susceptible to measles is someone who cannot provide acceptable presumptive evidence of immunity to measles. A person can be considered to have acceptable presumptive evidence of immunity to measles if they meet one of the following criteria:

• people born during or since 1966 who have documented evidence of receiving 2 doses of a measles-containing vaccine when both doses have been given at ≥ 12 months of age and at least 4 weeks apart (unless serological evidence indicates otherwise)
• people born before 1966 (unless serological evidence indicates otherwise)
• documented evidence of immunity
• documented laboratory definitive evidence of prior measles.

Prophylaxis

Susceptible contacts should be provided with either MMR vaccine or normal human immunoglobulin (NHIG) according to:

• time elapsed since exposure to an infectious case (where there has been ongoing exposure, such as with household contacts, the time since exposure should be calculated from the first contact during the infectious period)
• age
• previous MMR vaccination history
• current pregnancy or immunosuppression.

If contact with the infectious case occurred between 72 and 144 hours, immunoglobulin should be offered (see the next section).

Immunoglobulin prophylaxis

The recommended dose of NHIG is 0.2 mL/kg body weight (maximum dose = 15 mL) given by deep intramuscular injection. Pregnant women and eligible immunocompetent children receive this dose. Children who have immunodeficiency diseases such as leukaemia, lymphoma or HIV infection require a higher dose (0.5 mL/kg body weight, maximum dose = 15 mL).

Control of environment

Any room visited by a patient while they are infectious should be left vacant for at least 2 hours after the patient has left. This includes medical consulting rooms. Environmental clean-up is not generally recommended, although items contaminated with nasal and throat discharges should be disposed of carefully.

Outbreak measures for measles

Outbreaks in the community occur sporadically as a result of imported measles cases exposing local susceptible people. The epidemiology of outbreaks has changed with the introduction of childhood vaccination, and young adults are now at highest risk. Outbreaks in schools may still occur if there are significant numbers of unvaccinated students.

The department conducts detailed investigations of clusters of cases.

Special settings

Schools

Although outbreaks mainly affect unvaccinated children, highly vaccinated school populations have also been affected.

Cases are excluded from school and childcare for at least 4 days after rash onset.

Immunised contacts are not excluded. Unimmunised contacts should be excluded until 14 days after the first day of appearance of the rash in the last case.

If unimmunised contacts are vaccinated within 72 hours of their first contact with the first case or if they receive immunoglobulin within 144 hours of the contact, they may return to school.

During an outbreak, children and their siblings who are aged from 1 year to 18 months should receive their routine second dose of MMRV early (but not less than 4 weeks after their first dose).

Childcare

If there is a case of measles in a childcare setting where infants 6–12 months of age are present, they should be excluded from attendance for 14 days to interrupt local transmission. Infants can return if they receive MMR vaccination (9–12 months) within 72 hours of their first contact or if they receive immunoglobulin (6–12 months) within 144 hours.

Infants under 6 months should be excluded if the mother is a case or has no documented evidence of receiving two doses of a measles-containing vaccine when both doses have been given at ≥12 months of age and at least 4 weeks apart. If a mother can demonstrate protective immunity (that is, positive measles IgG), then the infant is considered immune and can attend.