For immune status (asymptomatic patient) = single serum for anti-measles IgG.
For investigation of possible infection (symptomatic patient) = acute and convalescent sera for anti-measles IgM and IgG. See also measles PCR
Incubation period 8-12 days
Infectivity to others During prodrome to 4 days after rash
Appearance of IgM 3-5 days post rash
Appearance of IgG 7-10 days post rash
Measles is an acute, highly communicable viral illness usually transmitted via respiratory secretions. There is a prodromal phase of 2 - 4 days with fever, conjunctivitis, coryza and Koplik spots on the buccal mucosa. The characteristic maculopapular rash appears on the 3rd to 7th day, spreads over 3-4 days from the head to the trunk to the extremities and lasts for up to one week. Complications include otitis media, pneumonia and encephalitis.
Anti-measles IgM is detectable 3-5 days after the appearance of the rash and usually falls to undetectable levels within 4-8 weeks. Anti-measles IgG is generally undetectable up to 7 days after rash onset, but subsequently peaks at about 14 days and usually remains detectable for life. Serology should be collected at the onset of illness and 10-14 days later.
A case of suspected measles should always be reported to the Medical Officer of Health (ph 09 623 4600), since even one case is considered an outbreak. If the patient is being admitted, airborne precautions are required. It is important that laboratory confirmation is attempted for accurate surveillance of this vaccine-preventable disease. Please note the vaccine history on the request form and collect nasopharyngeal samples and EDTA blood for measles PCR as well as serum for antibody testing.
Measles-mumps-rubella (MMR) vaccine is given at 15 months and 4 years of age. 5-10% of recipients do not seroconvert to the measles component after the first dose, but virtually all do after the second. Even though antibody levels decline over time, vaccine failure due to waning of protective immunity is rare. After the 1st dose of MMR, anti-measles IgM is detectable in 60-70% at 2-4 weeks and persists for several weeks, i.e. IgM positive tests during this time do not necessarily indicate infection due to wild measles virus. Anti-measles IgG is detectable in most by weeks 3-4.
After MMR, rash and high fever attributable to the vaccine have occurred in 1.6% and 1.4% respectively; both occurred in the second week.
Live attenuated measles-containing vaccine may provide some protection to immunocompetent, non-pregnant contacts of a measles case, if given within 72 hours of exposure. Immunoglobulin can also prevent or modify measles in susceptible persons and is recommended for susceptible household and nosocomial contacts at risk of developing severe measles, e.g. children younger than 1 year, the immunocompromised and pregnant women.
For further information on measles immunisation refer to the current Immunisation handbook under "Immunisation" at www.moh.govt.nz/healthtopics
For further information about airborne precautions, refer to the Infection Prevention & Control service.