Measles (Rubeola) Antibodies, IgM

The Measles (Rubeola) Antibodies, IgM assay, also referred to as measles IgM serology or Rubeola IgM, is used to identify recent or acute measles virus infection by demonstrating serum IgM antibodies. Interpretation incorporates the clinical presentation and illness timeline, and, when available, concurrent molecular detection from a respiratory specimen (PCR) in accordance with public health guidance.

Measles virus is a paramyxovirus transmitted by respiratory droplets and is highly contagious. Illness typically features fever, cough, coryza, conjunctivitis, enanthem (Koplik spots), and a morbilliform rash that begins on the head and spreads downward. Complications can include otitis media, bronchitis, pneumonia, diarrhea, encephalitis, and vision loss, with higher risk in immunocompromised persons, those who are undernourished, and individuals with vitamin A deficiency. Following infection, measles-specific IgM appears first, reaches peak levels within days, and then declines over subsequent weeks. IgG develops later and persists for years, including after vaccination. Absence of measurable IgM does not exclude very early disease; serology must be interpreted in relation to symptom timing and clinical findings. Testing for measles IgM is most informative in patients whose presentation is consistent with measles.