Parvovirus B19 and erythema infectiosum
Concise emergency‑medicine summary of the common presentations, key investigations, complications and immediate actions for parvovirus B19 infection (erythema infectiosum / “fifth disease” / “slapped‑cheek”), with emphasis on pregnant contacts, patients with haemolytic disease and the immunocompromised (UKHSA guidance).
Agent and typical syndromes
Parvovirus B19 is a non‑enveloped single‑stranded DNA virus that infects erythroid progenitors. Typical outcomes include:
- Erythema infectiosum: a common, usually mild childhood illness with sudden “slapped‑cheek” facial erythema followed by a maculopapular or reticular rash.
- Asymptomatic infection.
- Transient aplastic suppression leading to aplastic crises in patients with chronic haemolytic anaemias.
- Persistent anaemia or pure red cell aplasia in immunocompromised patients; pancytopenia in profoundly immunosuppressed hosts.
Infection usually confers long‑term immunity (IgG).
Epidemiology, incubation and infectivity
- Incubation for the rash illness is typically 4-20 days.
- Transmission is mainly via respiratory secretions and droplets.
- Infectivity is highest during the viraemic/prodromal phase (approximately up to 10 days before the rash). Patients are usually not infectious once the rash appears (UKHSA).
- Outbreaks are common in schools and childcare settings.