Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measures | Additional sources of information
Measles (Group A disease) must be notified immediately by telephone or fax followed by a written notification within five days.
School exclusion for cases and contacts is:
- cases should be excluded for at least four 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 seven days of the contact they may return to school.
Measles virus is a member of the genus Morbillivirus.
Clinical features of measles include prodromal fever, a severe cough, conjunctivitis, coryza and Koplik’s spots on the buccal mucosa. These are present for three to four 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 all the following features:
- generalised maculopapular rash, usually lasting three or more days, AND
- fever (at least 38°C if measured) present at the time of rash onset, AND
- cough, coryza, conjunctivitis and Koplik’s spots.
The characteristic red, blotchy rash appears on the third to seventh day. It begins on the face before becoming generalised and generally lasts four to seven days.
Complications can include otitis media, pneumonia and encephalitis. Sub-acute sclerosing panencephalitis (SSPE) develops very rarely as a late sequela.
Persons who have been previously immunised may present with non-classical features.
Measles infection (confirmed virologically) may rarely occur without a rash.
Method of 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% for samples taken 4–14 days after rash onset. If testing is negative for anti-measles IgM on a sample collected three days or less after rash onset, it should be repeated between 4–14 days after rash onset.
The diagnosis can also be confirmed by demonstration of a fourfold or greater change in measles antibody titre between acute and convalescent-phase sera. These should be obtained at least two weeks apart, with the tests preferably conducted in parallel at the same laboratory.
Serodiagnosis is not possible between eight days and eight weeks after measles vaccination. Suspected measles cases who have been recently vaccinated prior to their illness onset can only be confirmed as cases if they have an epidemiological link to a confirmed measles case or if a non-vaccine strain is identified in a clinical specimen by culture or molecular methods.
The incubation period is approximately ten days, but varies from seven to 18 days from exposure to the onset of fever. It is usually 14 days until the rash appears.
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 persons (herd immunity) if high enough coverage is achieved. Measles vaccine has several major effects on measles epidemiology. These include achieving 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. This is primarily because of underutilisation of the vaccine. In 2001 it was estimated that there were 30 million measles cases and 777 000 deaths. Most deaths occurred in developing countries, principally in Africa and Asia. Thirteen countries reported that routine measles vaccine coverage was below 50%. Large measles outbreaks continue to occur. These 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%) to achieve herd immunity. This allowed major measles outbreaks in many areas in 1993–94. In 1994 a second dose of measles-mumps-rubella (MMR) vaccine was introduced for a year’s cohort of children aged between 10 and 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 four years in 1999. After the measles control campaign an estimated 96% of children aged five to 12 years had received two doses of MMR.
Although the endemic spread of measles has now been interrupted in Australia, small outbreaks have continued to occur following importation 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.
Measles transmission is airborne by respiratory droplet nuclei spread or it can be transmitted by direct contact with infected nasal or throat secretions. The virus can persist in the environment for up to two hours. Transmission has been reported to people whose only apparent source of infection was a room presumably contaminated with measles virus when it had been occupied by a patient with measles up to two hours earlier.
Cases are infectious from slightly before the beginning of the prodromal period, usually five days prior to rash onset. They continue to be infectious until four days after the onset of the rash.
Natural infection provides lifelong immunity. A history of prior measles infection should be confirmed serologically before vaccination is deferred as reports of clinical measles infection are not always accurate.
Vaccination at 12 months of age produces a protective antibody in approximately 95% of recipients. The second dose of vaccine, recommended at 4 years, increases protection to approximately 99% of recipients.
Live attenuated measles vaccine is recommended for all persons born after 1966 unless specific contra-indications to live vaccines exist.
It is recommended that this vaccine be given as measles-mumps-rubella (MMR) vaccine at 12 months of age and a second dose at four years of age (prior to school entry). The second dose is not a booster but is designed to vaccinate the approximately five per cent of children who do not seroconvert to measles after the first dose of vaccine.
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 one 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.
Unimmunised health care workers, including medical practice staff, born after 1966 are at high risk of measles infection. The measles vaccination status of all health care workers measles should be assessed prior to commencing 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 isolated 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 child care for at least four days after the onset of the rash.
The Department of Health actively investigates all suspected measles cases to confirm the diagnosis, identify the source of infection, identify other cases, and to identify and protect susceptible contacts in the community.
Control of contacts
The Department of Health will trace and manage susceptible community contacts of cases. The responsibility of identifying and protecting susceptible contacts exposed in health care institutions, such as medical practices or emergency departments, is the responsibility of the individual institution.
Control measures require:
1. Identification of susceptible contacts:
- make a list of other people who attended the same area at the same time or within two hours after the visit of the measles patient, including staff
- determine which of the contacts are likely to be susceptible to measles (see below).
2. Protection of susceptible contacts of a measles patient with:
- MMR if within 72 hours of first contact with the patient
- immunoglobulin if longer than 72 hours but within seven days from contact (see below); then offer MMR three months later.
Susceptible contacts are best identified by excluding contacts not considered to be at risk. These are:
- children aged one to four years who have documented evidence of having had one measles vaccine dose
- persons born after 1966 who have had two measles vaccine doses
- susceptible contacts who have documented evidence of having had at least one measles vaccine dose do not require immunoglobulin but should be offered a second MMR dose
- persons born before 1966, as they are likely to have natural immunity
- persons with documented evidence of immunity through vaccination or natural infection.
Prophylaxis for contacts under 12 months of age
- Infants less than six months of age should not be given MMR and should not be offered immunoglobulin unless the mother is a case, or the mother has been tested and found to have no measles immunity.
- Infants six to nine months of age should not be given MMR but should be offered immunoglobulin if within seven days from first contact with a case.
- Infants between nine and twelve months of age should be offered early MMR if within 72 hours of first contact with a case, and receive a further dose at 12 months of age or four weeks after the first dose, whichever is later. This second dose does not replace the routine dose of MMR at four years but is given because children under 12 months have a lower likelihood of becoming immune (seroconverting) after measles vaccination.
If contact with the infectious case occurred between 72 hours and seven days, immunoglobulin should be offered (see below).
The recommended dose of immunoglobulin is 0.2 mL/kg body weight (maximum dose = 15 mL) given by deep intramuscular injection. 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 infectious should be left vacant for at least two hours after the patient has left. This includes medical consulting rooms. Evironmental clean-up is not generally recommended, although items contaminated with nasal and throat discharges should be disposed of carefully.
Outbreaks in the community setting 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, with young adults now at highest risk. Outbreaks in schools may still occur if there are significant numbers of unvaccinated students.
The Department of Health conducts detailed investigations of clusters of cases.
Although outbreaks mainly affect unvaccinated children, highly vaccinated school populations have also been affected.
Cases are excluded from school and child care for at least four 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 seven days of the contact they may return to school.
During an outbreak, children and their siblings who are aged between one and four years should receive their routine second dose of MMR early (but not less than four weeks after their first dose). They are then considered to have completed their MMR vaccination schedule and so do not need a further dose at four years of age.
If there is a case of measles in a child care setting where infants between six to twelve 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 seven days.
It is not necessary for infants under six months to be excluded unless the mother is a case, or where the mother is aware she has no protective immunity.