What is the measles virus?

The measles virus is a type of paramyxovirus. It contains 2 proteins on the outer membrane. The first is the fusion protein (F), which is responsible for the fusion of the virus to the host cell membranes, viral penetration, and the destruction of red blood cells. The second is the hemagglutinin protein (H), which helps in the absorption of the virus into cells. The core contains single-stranded RNA (ribonucleic acid).1

Environmental factors such as heat, sunlight, acidic conditions, ether, and trypsin may inactivate the virus. The virus typically survives in the air or on objects and surfaces for less than 2 hours.1

How is measles transmitted?

Measles is highly contagious. Transmission occurs primarily by direct contact via respiratory droplets from an infected person to a susceptible individual from coughing, sneezing, or close personal contact. The virus is still active and contagious for up to 2 hours in the air or on infected surfaces. The virus can be transmitted several days before to several days after development of a rash from an infected individual.2

What are the pathogenesis and clinical features of measles infection?

Measles infection affects the entire body. Although the first site of infection is the lining of the nasopharynx, after viral invasion and replication in the respiratory epithelium and regional lymph nodes, the infection enters the bloodstream, which is known as primary viremia. Further infection and replication at regional and distal sites can lead to a second viremia and subsequent infection of other body organs.1

General Clinical Features of Measles Infection by Phases1

Phases Characteristics

Incubation Phase

  • Days 10–12 duration from exposure

Prodrome Phase
(early signs and
symptoms of disease)

  • Days 12–16 from exposure
  • Stepwise fever (which may peak at 103°F–105°F)
  • Conjunctivitis (pink eye)
  • Coryza (cold symptoms: runny nose and congestion)
  • Cough
  • Koplik spots (characteristic blue and white spots on the inner lining of cheeks, mouth, and lips that may be bright red; appear 1–2 days before and 1–2 days after the measles rash)

Manifestation Phase

  • Days 14–21 from exposure
  • Commonly forms a rash
    • First appears around the hairline approximately 2–4 days after onset of symptoms
    • Spreads down to cover the face, trunk, limbs, and hands and feet over a few days
    • The rash is initially maculopapular (flat red area) and tends to become confluent (appearing together) as it spreads, especially on the face and neck

What are the complications of measles?

Complications of measles can include diarrhea, pneumonia, otitis media, and rarely, encephalitis, seizures, and death. Approximately 30% of measles cases can have complications.1,3

Measles Complications by Incidence Based on Surveillance Data in the United States Between 1985–19921


Incidence Rates




  • Most common complication

Otitis media
(inflammation of the ear)


  • Usually only in children



  • Common cause of measles-related death

(inflammation of the brain)


  • Usually occurs 6 days after rash
  • Symptoms include fever, headache, vomiting, stiff neck, drowsiness, convulsion, and coma



  • This can occur with or without fever



  • Risk is highest in young children and adults; mostly attributed to pneumonia in children and encephalitis in adults

In pregnant women, measles can result in higher risk of miscarriage, premature labor, and low birth weight. There is lack of evidence to attribute measles illness to associated birth defects.1

Complications are more common among children under 5 years old and adults 20 years and older.1

Complications From Measles Are More Common Among Young Children and Adults1


Incidence (%)

Age Group (years)


How is measles diagnosed?

Although identification of the measles virus is not routinely recommended, identification and verification are helpful for geographic tracking or epidemiologic surveillance.1

A measles diagnosis can be made through analyzing samples from urine, nasal passages, blood, and throat. For every suspected case, samples for virus culture should be collected and sent to state public health laboratories or the Centers for Disease Control and Prevention (CDC). Samples should be collected within 7–10 days after rash onset.1

How does geography affect the disease epidemiology of measles?

Temperate and Tropical Climates Have Different Effects On the Disease Pattern of Measles and When There Are Upticks In the Number of Measles Patients

In regions with warmer summers and cooler winters, measles is usually seen in the late winter and early spring.1,4


In tropical climates, higher incidences occur after the rainy season.4

Downloadable Resource

The resource below has been created to help your patients, their parents, or their legal representatives, learn about measles while they wait in the doctor’s office.

What you should know about measles
PDF about measles that you can download and share with patients, their parents, or their legal representatives.

CDC Disease Information

DISCLAIMER: By clicking on the link below, you will be directed away from to another website. Merck does not review or control the content of the site to which the hyperlink connects; therefore, the hyperlink does not constitute an endorsement by Merck.

CDC, Centers for Disease Control and Prevention


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CDC Information

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  1. Centers for Disease Control and Prevention (CDC). Measles. In: Hamborsky J, Kroger A, Wolfe S, eds. Epidemiology and Prevention of Vaccine-Preventable Diseases. 13th ed. Washington, DC: Public Health Foundation; 2015:209–230. Accessed January 22, 2020.


  1. World Health Organization (WHO). Measles. Updated December 5, 2019. Accessed January 22, 2020.


  1. Gershon AA. Measles virus (rubeola). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas and Bennett’s Principles and Practice of Infectious Diseases. Vol 2. 9th ed. Philadelphia, PA: Elsevier Saunders; 2019:2110-2116.


  1. World Health Organization (WHO). International travel and health. Accessed January 22, 2020.

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