Written by Clay Smith
The U.S. is currently in a measles outbreak. So, don’t miss this quick spoon-feed refresher. You will learn something new.
Why does this matter?
Measles is a mild, self-limited illness in most people. It was temporarily eradicated in the U.S. as of 2000, but more and more cases are being seen as families choose not to vaccinate. There have been nearly 800 cases in the U.S. already in 2019.
You need to know about measles
Given the recent outbreak, someone who reads JournalFeed is likely to see a case. We need to be ready. Especially review the images at the end.
How does measles present?
Peak incidence is in the spring and summer, highest in March, but may occur year round.
Unvaccinated populations, travelers to an endemic area, or immunocompromised patients are most at risk.
Incubation period is 6-21 days, median 13.
Fever starts first, up to 40°C by day 5.
Conjunctivitis, cough, coryza (copious nasal drainage) begins next (Image 1).
Koplik spots on the buccal mucosa, usually opposite the molars, appear 48h prior to rash (Image 2). Spots may be anywhere on the oropharyngeal mucosa, such as the soft palate. Cervical adenopathy is common.
Rash appears last, starting on the face, especially along the hairline behind the ears, spreading across the face, down the neck, onto the trunk; spares palms and soles, morbilliform in appearance (of course), blanching at first, then non-blanching. Rash resolves over the next 6 days. Images 3 and 4.
Labs may show eosinophilia or elevated transaminases.
What are the complications of measles?
Complications occur in 30%.
Diarrhea occurs in 8%.
Global immunosuppression and secondary bacterial infections are common, i.e. otitis media - 7% of all patients; also staphylococcal, streptococcal, or H. influenzae infections.
Pneumonia occurs in 6% and is the most common cause of death.
Encephalitis occurs in 1/1000. Read this heartbreaking account of measles encephalitis by Roald Dahl about his 7-year-old daughter and his plea for vaccination. “In an hour, she was unconscious. In twelve hours she was dead.”
Acute demyelinating encephalomyelitis (ADEM) occurs in 1/1000, with 10-20% mortality rate.
Rarely, delayed onset subacute sclerosing panencephalitis occurs (5-10/million cases per this review but far more common per the Lancet review), which is a progressive neurological decline that is universally fatal.
Where does measles occur in the world?
Measles occurs around the world. India has the highest incidence.
“In many parts of the world, including Europe, Central and South America, Asia, the Pacific and Africa, the disease remains endemic.”
Indonesia had a drop in vaccination rates and subsequent spike in cases.
The U.S. is currently in its worst outbreak in decades, due to undervaccination.
How is measles diagnosed?
The initial diagnosis is clinical, as above.
Confirmation is by saliva, mouth, throat, or blood samples with PCR-based testing. My state (TN) recommends a throat swab sent in viral transport media.
How is measles managed in the ED?
Patients should be placed in isolation using airborne precautions. An N-95 mask, gown, and gloves are needed.
Patients should be thoroughly examined and treated for bacterial superinfection or other complications. Most treatment is symptomatic and done at home.
“Given that vitamin A deficiency predisposes to severe and complicated measles, two oral doses [given over two consecutive days] of vitamin A 200,000 IU (100,000 IU if age 6–11 months, 50 000 IU if under 6 months) is recommended for all children with acute measles and to all cases of severe infection with measles. A third dose is given 2–4 weeks later.”
Local infection control should be notified, as well as state public health officials. This is a reportable illness.
Susceptible family contacts or other known contacts should be vaccinated with two doses of MMR a month apart as soon as possible.
How contagious is measles?
Measles is one of the most contagious pathogens, able to cause disease via airborne particles up to two hours after an infected patient has left the room, with a 90% attack rate.
In other words, if you are susceptible and exposed, there is a 90% chance you will get it.
How effective is the measles vaccine?
It is 90% effective after one dose of MMR and essentially 100% effective with two, spaced a month apart.
It is usually given at 12-15 months and then 4-6 years.
How should measles exposure be managed if vaccine status is uncertain?
It is safe to give MMR even if vaccine status is unknown.
It does not have proven safety in pregnancy and is usually avoided. It is important to be vaccinated prior to pregnancy, as transplacental antibody protection is strong.
What precautions are needed if traveling to a high incidence area?
Special caution is needed, “in Africa, especially in Nigeria, in China, the Philippines and the Middle East, including Yemen.”
Unvaccinated people should get two MMR vaccines a month apart.