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Microbiology · Respiratory RNA viruses

Measles virus !

  • Virus
  • Enveloped
  • Airborne
  • Exam priority: high

One of the most contagious viruses known. It causes fever, cough, red eyes and a rash that spreads down from the face; the vaccine prevents it.

Updated 2026-11-01

Also called: rubeola, morbillivirus

At a glance

Shape
Pleomorphic spherical
Genome
Single-stranded, negative-sense, non-segmented RNA
Envelope
Enveloped
Family
Paramyxoviridae, genus Morbillivirus
Size
Pleomorphic, about 150 nm or more (up to several hundred nm)

Morphology

  • Envelope with haemagglutinin (H) and fusion protein (F), which forms multinucleated giant cells
  • A single serotype, so the vaccine gives lasting protection

Transmission

  • Aerosols that stay in the air for up to two hours
  • Droplets and respiratory secretions
  • Contagious from four days before to four days after the rash
  • One person can infect many susceptible others

Reservoir: Humans only, which makes elimination possible

Isolation precautions

What the care team adds to standard precautions.

Airborne
N95 respirator and a negative-pressure room.

Virulence factors

  • Infects lymphocytes and dendritic cells (SLAM/CD150 receptor) and then epithelium (nectin-4)
  • Immunosuppression and "immune amnesia": it erases memory against other infections for months or years
  • Warthin–Finkeldey giant cells in lymphoid tissue
  • Persistent defective virus in the brain: subacute sclerosing panencephalitis

Diseases it causes

  • Measles, with pneumonia, otitis, diarrhoea, encephalitis and subacute sclerosing panencephalitis years later Measles →

Clinical picture

  • Prodrome of high fever, cough, coryza and conjunctivitis
  • Koplik spots: whitish dots on the buccal mucosa, pathognomonic
  • Maculopapular rash that starts on the face and behind the ears and moves down
  • Complications: otitis, pneumonia, croup, diarrhoea, encephalitis, blindness (with vitamin A deficiency)
  • Subacute sclerosing panencephalitis, rare and fatal, years later

Diagnosis

  • Specific serum IgM
  • RT-PCR on a throat or nasopharyngeal swab and urine, taken at first contact
  • Genotyping to tell wild-type virus from vaccine virus
  • Every suspected case is immediately notifiable

Treatment

There is no specific antiviral: supportive care and vitamin A (retinol) for children, which lowers complications and deaths. Secondary bacterial infections are treated with antibiotics.

Drug class only; doses and regimens are set by the clinician from the current guideline.

Prevention

  • MMR vaccine (measles, mumps, rubella), live attenuated, in two doses
  • Ring vaccination around each case
  • Airborne precautions: negative-pressure room and an N95 respirator for all staff
  • Isolation until four days after rash onset

Vaccine: Live attenuated MMR vaccine; it is in Colombia's PAI with one dose at one year and a booster in early childhood.

Test yourself

Think of the answer, then tap the question to see it.

Which oral finding is pathognomonic for measles?

Koplik spots, whitish dots on a red base on the buccal mucosa.

Which isolation precautions does a measles patient need?

Airborne precautions: a negative-pressure isolation room and an N95 respirator for all staff, until four days after the rash.

Which late neurological complication does measles cause?

Subacute sclerosing panencephalitis, a fatal degenerative disease that appears years after infection.

Which supplement is given to children with measles, and why?

Vitamin A, because it lowers severity, eye complications and mortality.

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← Back to the group: Respiratory RNA viruses

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Measles (World Health Organization (WHO), 2026); Clinical Overview of Measles (CDC, 2025); Colombia recertificada como país libre de sarampión y rubéola (Instituto Nacional de Salud (INS) Colombia, 2022); Measles (Pan American Health Organization (PAHO), 2026).

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Representative model, for educational purposes only.