Measles

General paediatrics, Infectious disease

Notifiable.

Currently not an outbreak in Scotland but surging numbers in England (esp West Midlands and London) October 2023-January 2024, with worldwide outbreaks – Kazhakstan, Yemen, Ethiopia, Pakistan.

Extremely infectious – in a vulnerable population, you can expect 15-20 more cases per index case (R0 number). Incubation period is 7-21 days, typically 10-12 days. Infectious period is 4 days before to 4 days after onset of rash. Starts with a prodrome of cough, coryza, conjunctivitis and fever lasting 2-6 days (peaks at day 4-5). Then the rash appears: brick red, maculopapular, starts behind ears, spreads from face on to trunk and then everywhere including palms/soles. Discrete spots may then coalesce. With time the rash may darken (“stain”) and may desquamate. The child is typically irritable – compare other common childhood rashes.

Koplik’s spots are pathognomic but easily missed as they appear early in the illness, disappearing within a few days of the rash starting. They are grey or white spots on the buccal mucosa opposite the 2nd molars.

Case definition is:

  • a fever (temperature 38ºC or higher) and
  • generalised maculopapular rash lasting three days or longer and
  • either cough, coryza or conjunctivitis.

Diagnosis is by oral fluid test else throat swab (or urine) for PCR. Send blood for IgG/M too.

Complication

Significant effect on immune function.

Measles pneumonia most common cause of mortality.

Encephalitis well recognised. Roald Dahl’s daughter Olivia died of it in the 60s and he was a strong supporter of immunisation thereafter.

Management

  • Check vulnerable contacts. Risk window is 4 days prior to rash, to 4 days after onset of rash (peak infectivity before rash appears).
    • Immunosuppressed (biologics or chemo) Group A – may have had good immune response to vaccination earlier in life. Check Measles IgG if in doubt. Susceptibility depends on age, history of previous measles infection, vaccine status. See table 3 below.
    • Immunosuppressed Group B – known vulnerable else unlikely to have adequate antibody levels. Check Measles IgG and treat if negative or unable to check (some will just need IVIG regardless).
    • Pregnant women – even equivocal measles IgG considered protected (neutralisation assays show detectable antibody). Check if only one measles vaccine given or unvaccinated (allow 6 days for result). HNIG used.
    • Infants under 6 months get HNIG as little transplacental transfer of measles antibody, and wane. 6-8 months old with household contact considered high risk and should get HNIG, for other exposure can get MMR.
    • From 9 months onwards, MMR, ideally within 3 days. Beyond 3 days may still help protect against other potential exposures in outbreak.
    • immunosuppressed but also infants and pregnant women. There is not an explicit definition for close contact. Ideally vaccination should be offered within 3 days.
      • Pregnant vaccinated women should be fine, if in doubt do rapid antibody levels, give HNIG (Human Normal Immunoglobulin, NOT MMR) if necessary, repeat serology at 3/52.
      • Infants under 6/12 should get HNIG, unless mother has had natural measles (or born before 1970!). Else MMR, unless 6-8/12 old and a household contact or high risk.
    • IVIG/HNIG should be given within 72 hours of exposure (up to 6 days). Protects for 3 weeks, after which another dose required if further exposure. Dose for IM is 0.6mg/kg up to a maximum of 1,000mg
  • Respiratory protective equipment should be worn when caring for confirmed or suspected cases viz FFP3 respirator.

[HPA Guidance 2024]

Vaccination

Measles now endemic again in England and many European countries, with cases increasing year on year with only a slight reversal during lockdown. Before vaccines, pretty much inevitable part of childhood.

Andrew Wakefield in 1998 didn’t help – no immediate problem with his false paper (due to herd immunity), first death not until 2006, at which point rate 13x higher than pre-Wakefield. Vaccine hesitancy continues to be one of the biggest global health challenges of our time.

MMR clinical symptoms occur 7-14 days post-vaccination. Very rare after booster. Tends to be mild fever, rash and conjunctivitis.

Porto Outbreak

March-April 2018, 96 confirmed cases in a hospital in Porto, Portugal. Mostly vaccinated Health care workers!!!

Atypical presentations – mac-pap rash only, low fever.

Chances of an “escape variant” not covered by vaccine almost zero.