Which virus is classically associated with the 'Fifth disease' rash?

• A. Parvovirus B19
• B. Varicella
• C. Measles
• D. Rubella

Answer: (A)

Fifth disease is erythema infectiosum, classically caused by Parvovirus B19. In children, it produces a distinctive bright red facial rash that looks like a “slapped cheek,” followed by a lace-like, reticular rash on the trunk and limbs. Adults may experience arthralgias. The virus specifically infects erythroid precursor cells, briefly halting red blood cell production, which explains why people with hemolytic conditions can have a more serious or prolonged impact, and why fetal infection can risk anemia and hydrops. The other viruses have different rash patterns: Varicella causes vesicular lesions in various stages; Measles presents with fever, cough, coryza, and conjunctivitis followed by a maculopapular rash starting at the face, and Rubella typically causes a lighter, fine maculopapular rash with posterior auricular lymphadenopathy. The classic facial “slapped cheek” plus the subsequent lace-like body rash point to Parvovirus B19 and Fifth disease.