Erythema infectiosum (fifth disease, parvovirus B19) !

A mild childhood viral rash caused by parvovirus B19: bright red 'slapped' cheeks, then a lacy rash on the body. Risky in pregnancy and blood disorders.

Updated 2026-11-01

Structures involved

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Skin

Microorganisms that cause it

Parvovirus B19

Why it happens

What it is

A common, usually mild viral exanthem of school-age children caused by human parvovirus B19. After a short prodrome it produces red cheeks and then a lace-like rash on the limbs and trunk. The same virus can stop red-cell production, which matters in people with haemolytic anaemias, immunosuppression or pregnancy.

Who gets it

Worldwide, with outbreaks in schools in late winter and spring. Most adults have antibodies from childhood infection. It is not a notifiable disease in Colombia, so local data are limited; outbreaks are reported in schools and nurseries across Latin America.

Causes

Human parvovirus B19, a small single-stranded DNA virus (genus Erythroparvovirus)
Spread mainly by respiratory droplets; also by blood products and from mother to fetus across the placenta
The virus binds the P antigen (globoside) on erythroid progenitor cells in the bone marrow

Risk factors

School or day-care attendance, and working with young children
Household contact with an infected child
Chronic haemolytic anaemia (sickle cell disease, hereditary spherocytosis, thalassaemia): risk of transient aplastic crisis
Immunosuppression (leukaemia, transplant, HIV): risk of chronic anaemia
Pregnancy without prior immunity, especially in the first half

Pathophysiology

Parvovirus B19 infects and kills erythroid precursor cells, so red-cell production stops for about a week. Healthy children barely notice this, but people whose red cells already live a short time develop sudden severe anaemia. The rash and joint pain appear later and are immune-complex mediated, so by the time the rash shows the child is usually no longer contagious.

Classification

Classic erythema infectiosum (children)
Arthropathy (mostly adult women)
Transient aplastic crisis (chronic haemolytic anaemia)
Chronic pure red-cell aplasia (immunocompromised)
Fetal infection with anaemia and hydrops fetalis

Symptoms and signs

Mild prodrome: low fever, runny nose, headache, malaise
Bright red 'slapped-cheek' rash with relative sparing around the mouth
A few days later, a lacy, reticular rash on the arms, legs and trunk that may itch
The rash can fade and reappear for weeks with heat, sunlight or exercise
Symmetric joint pain and swelling of the hands, wrists and knees, more often in adults
Many infections cause no symptoms at all

Diagnosis

Clinical: Usually a clinical diagnosis from the slapped-cheek face followed by a lacy body rash in a well child.
Tests: Testing is reserved for high-risk patients: parvovirus B19 IgM (and IgG for immunity) in pregnancy, PCR for viral DNA in the immunocompromised, and a blood count with a very low reticulocyte count in aplastic crisis.
Imaging: Not needed in children. After infection in pregnancy, serial fetal ultrasound with middle cerebral artery Doppler looks for fetal anaemia and hydrops.

Differential diagnosis

Rubella and measles
Roseola (exanthem subitum)
Scarlet fever
Drug eruption
Juvenile idiopathic arthritis or lupus when joint symptoms dominate

Goal of treatment

Relieve symptoms in healthy children and detect and treat severe anaemia early in high-risk groups.

Treatment

Conservative: Rest, fluids and fever or pain relief with paracetamol or NSAIDs; children may attend school once the rash appears, because they are no longer contagious.
Acute: Transient aplastic crisis is treated in hospital with red-cell transfusion as needed and close monitoring of the blood count.
Medical: Intravenous immunoglobulin is used for chronic parvovirus anaemia in immunocompromised patients.
Procedure: Severe fetal anaemia is managed in a specialised centre with intrauterine blood transfusion.
Follow-up: Pregnant women with infection are followed with serial ultrasound for several weeks; patients in aplastic crisis need droplet isolation because they remain contagious.

Complications

Transient aplastic crisis in chronic haemolytic anaemia
Chronic pure red-cell aplasia in immunocompromised patients
Fetal anaemia, hydrops fetalis and miscarriage
Self-limited arthritis, mostly in adults

Prognosis

Excellent in healthy children; the illness clears on its own and gives lifelong immunity. Outcomes in aplastic crisis and fetal infection depend on early recognition and transfusion.

Prevention

Hand washing and covering coughs and sneezes
Pregnant women and people with haemolytic anaemia should avoid outbreak settings and consult early if exposed
Droplet precautions for hospitalised patients with aplastic crisis or chronic infection

Test yourself

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

Which cells does parvovirus B19 infect?

Erythroid progenitor cells in the bone marrow, through the P antigen (globoside).

Is a child with the slapped-cheek rash still contagious?

Usually not; the rash is immune-mediated and appears after the infectious period.

What complication does parvovirus B19 cause in sickle cell disease?

Transient aplastic crisis: sudden severe anaemia with a very low reticulocyte count.

What fetal complication is feared after maternal infection?

Severe fetal anaemia leading to hydrops fetalis, and miscarriage.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Fifth disease (MedlinePlus (U.S. National Library of Medicine), 2025); About Parvovirus B19 (Centers for Disease Control and Prevention (CDC), 2025).

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