GPAtlas🧭 When to suspect
Parvovirus B19 causes erythema infectiosum (fifth disease, "slapped cheek syndrome"), a common and usually trivial childhood infection. Suspect it in a well child with a bright red rash over both cheeks – as if slapped – classically sparing the nasal bridge and perioral skin, often followed a few days later by a lacy, reticular (net-like) rash on the trunk and limbs. A mild prodrome of low-grade fever, coryza, headache and malaise usually precedes the rash.
In adults the facial rash is frequently absent and the dominant feature is an acute symmetrical arthralgia or arthritis of the small joints, especially in women. Infection is commonest in children aged 6–10, peaks in spring, and recurs in the community every 3–4 years – the UK Health Security Agency (UKHSA) reported a marked rise from late 2023 into 2024. Around 50–70% of adults are already immune. The rash is clinically indistinguishable from rubella, which must also be considered in any pregnant woman with a rash.
The whole clinical task is to recognise a benign illness in the well, while identifying the three groups in whom it is dangerous: pregnant women, those with chronic haemolytic anaemia, and the immunocompromised.
| Host group | Why it matters | Action |
|---|---|---|
| Healthy child or adult | Benign, self-limiting erythema infectiosum | Reassure; symptomatic care; no exclusion once the rash appears |
| Pregnant woman (greatest risk < 20 weeks) | Vertical transmission → fetal anaemia, hydrops, miscarriage or intrauterine death | Check immunity urgently (serology); refer Fetal Medicine if infection confirmed |
| Chronic haemolytic anaemia (sickle cell, thalassaemia, hereditary spherocytosis) | Transient aplastic crisis – sudden arrest of red-cell production | Urgent FBC and reticulocytes; same-day admission for transfusion if anaemic |
| Immunocompromised (chemotherapy, transplant, HIV) | Persistent infection → chronic red-cell aplasia | Specialist assessment; intravenous immunoglobulin |
|
⚠️ Common pitfall In an adult – often the parent of a child with slapped cheek – an acute symmetrical polyarthralgia of the hands, wrists and knees with no facial rash is easily mislabelled as early rheumatoid arthritis. Ask about recent contact with an affected child and check parvovirus B19 serology before committing to an inflammatory-arthritis pathway. B19 arthropathy is self-limiting, though it may persist for several weeks. |
Source: UK Health Security Agency (UKHSA) · NHS
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