Measles

Measles
Other names	Morbilli, rubeola, red measles, English measles[1][2]
A child showing a day-four measles rash
Specialty	Infectious disease
Symptoms	Fever, cough, runny nose, inflamed eyes, rash[3][4]
Complications	Pneumonia, seizures, encephalitis, subacute sclerosing panencephalitis, immunosuppression, hearing loss, blindness[5][6]
Usual onset	10–12 days after exposure[7][8]
Duration	7–10 days[7][8]
Causes	Measles virus[3]
Prevention	Measles vaccine[7]
Treatment	Supportive care[7]
Frequency	20 million per year[3]
Deaths	140,000+ (2018)[9][10]

Measles (probably from Middle Dutch or Middle High German masel(e) ("blemish, blood blister"))^[11] is a highly contagious, vaccine-preventable infectious disease caused by measles virus.^{[3][5][12][13][14]} Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days.^[7][8] Initial symptoms typically include fever, often greater than 40 °C (104 °F), cough, runny nose, and inflamed eyes.^[3][4] Small white spots known as Koplik's spots may form inside the mouth two or three days after the start of symptoms.^[4] A red, flat rash which usually starts on the face and then spreads to the rest of the body typically begins three to five days after the start of symptoms.^[4] Common complications include diarrhea (in 8% of cases), middle ear infection (7%), and pneumonia (6%).^[5] These occur in part due to measles-induced immunosuppression.^[6] Less commonly seizures, blindness, or inflammation of the brain may occur.^[5][7] Other names include morbilli, rubeola, red measles, and English measles.^[1][2] Both rubella, also known as German measles, and roseola are different diseases caused by unrelated viruses.^[15]

Measles is an airborne disease which spreads easily from one person to the next through the coughs and sneezes of infected people.^[7] It may also be spread through direct contact with mouth or nasal secretions.^[16] It is extremely contagious: nine out of ten people who are not immune and share living space with an infected person will be infected.^[5] Furthermore, measles's reproductive number estimates vary beyond the frequently cited range of 12 to 18.^[17] The NIH quote this 2017 paper saying: "[a] review in 2017 identified feasible measles R₀ values of 3.7–203.3".^[18] People are infectious to others from four days before to four days after the start of the rash.^[5] While often regarded as a childhood illness, it can affect people of any age.^[19] Most people do not get the disease more than once.^[7] Testing for the measles virus in suspected cases is important for public health efforts.^[5] Measles is not known to occur in other animals.^[16]

Once a person has become infected, no specific treatment is available,^[16] although supportive care may improve outcomes.^[7] Such care may include oral rehydration solution (slightly sweet and salty fluids), healthy food, and medications to control the fever.^[7][8] Antibiotics should be prescribed if secondary bacterial infections such as ear infections or pneumonia occur.^[7][16] Vitamin A supplementation is also recommended for children.^[16] Among cases reported in the U.S. between 1985 and 1992, death occurred in only 0.2% of cases,^[5] but may be up to 10% in people with malnutrition.^[7] Most of those who die from the infection are less than five years old.^[16]

The measles vaccine is effective at preventing the disease, is exceptionally safe, and is often delivered in combination with other vaccines.^[7][20] Vaccination resulted in an 80% decrease in deaths from measles between 2000 and 2017, with about 85% of children worldwide having received their first dose as of 2017.^[16] Measles affects about 20 million people a year,^[3] primarily in the developing areas of Africa and Asia.^[7] It is one of the leading vaccine-preventable disease causes of death.^[21][22] In 1980, 2.6 million people died from measles,^[7] and in 1990, 545,000 died due to the disease; by 2014, global vaccination programs had reduced the number of deaths from measles to 73,000.^[23][24] Despite these trends, rates of disease and deaths increased from 2017 to 2019 due to a decrease in immunization.^[25][26][27]