Is Fifth Disease Contagious?
Yes, fifth disease (erythema infectiosum) is highly contagious, but only during the early phase of illness before the characteristic rash appears—once the rash develops, patients are no longer infectious and do not require isolation. 1, 2
Transmission Dynamics
Fifth disease is caused by human parvovirus B19 and spreads through respiratory droplets when infected individuals cough, sneeze, or talk. 1, 2 The virus follows a pattern similar to other respiratory infections, requiring close contact for transmission. 3
Key Contagious Period
- Maximum infectivity occurs during the prodromal phase (before the rash appears), when patients have mild cold-like symptoms such as low-grade fever and malaise. 1
- Once the characteristic "slapped cheek" rash appears, the patient is no longer contagious and can return to school or work without risk of spreading infection. 1, 2
- This creates a significant public health challenge because most transmission occurs before the disease is clinically recognized. 1
Transmission Routes
The virus spreads primarily through:
- Respiratory droplets from coughing and sneezing, requiring close proximity (within 1 meter) to an infected person. 3
- Direct contact with respiratory secretions, including contaminated hands touching the nose or eyes. 3
- Contaminated surfaces (fomites) can harbor the virus temporarily, though this is a less common route than direct droplet transmission. 3
Clinical Context for Contagiousness
Most infections are subclinical or mild, meaning many infected individuals transmit the virus without knowing they are sick. 4 In one family study, the mother had a subclinical infection while still being infectious, demonstrating that absence of symptoms does not mean absence of contagiousness during the early phase. 4
Age-Related Presentation
- Children typically develop the classic rash and are the primary reservoir for community spread. 2
- Adults more commonly experience joint symptoms (arthropathy) rather than the characteristic rash, but remain contagious during the prodromal phase. 2, 4
Special Populations at Risk
Pregnant Women
Pregnant women exposed to fifth disease require careful evaluation, as the virus can cross the placenta and cause fetal complications including hydrops fetalis, severe anemia, and spontaneous abortion, though the absolute risk is low. 1
- Check maternal immune status (IgG antibodies) immediately after exposure. 1
- If IgG positive, reassure the patient—she is immune and the fetus is protected. 1
- If IgG negative (non-immune), serial ultrasound monitoring for fetal hydrops is recommended, though most exposed fetuses remain unaffected. 1
Immunocompromised Patients
Patients with weakened immune systems can develop chronic parvovirus B19 infection with persistent anemia, as they cannot mount an adequate antibody response to clear the virus. 2
Patients with Hemolytic Anemia
Those with sickle cell disease or other hemolytic anemias can develop transient aplastic crisis when infected, as the virus temporarily halts red blood cell production. 2
Practical Infection Control
Standard respiratory precautions are sufficient for managing fifth disease in healthcare and school settings. 3
- Exclude symptomatic children from school only during the prodromal phase if they have fever or appear ill. 1
- Once the rash appears, exclusion is unnecessary because the child is no longer contagious. 1
- Healthcare workers should use standard droplet precautions when caring for patients with suspected parvovirus B19 during the acute febrile phase. 3
- Hand hygiene after contact with respiratory secretions is essential to prevent indirect transmission. 3
Common Pitfall
The most common error is unnecessarily isolating children after the rash appears. This is both medically unnecessary (they are not contagious) and can cause undue anxiety for families. 1 The contagious period has already passed by the time the diagnosis is clinically apparent, making outbreak control challenging in schools and daycare settings. 1