In this episode, we tackle the clinical mischief of Parvovirus B19, a common viral infection with a surprisingly wide range of manifestations—from the classic “slapped cheek” rash of erythema infectiosum to aplastic crises in children with hemolytic anemias and fetal hydrops in pregnant contacts. We’ll break down the virology, epidemiology, clinical presentation, and complications of Parvovirus B19. You’ll also learn how to manage exposures in the emergency department, especially when the child has a pregnant caregiver, and why isolation isn’t always necessary once the rash shows up.

Learning Objectives

Describe the classic and atypical clinical presentations of Parvovirus B19 infection in pediatric patients, including erythema infectiosum, arthropathy, transient aplastic crisis, and chronic anemia in immunocompromised hosts.
Understand the epidemiology and transmission timeline of Parvovirus B19, especially its seasonal peaks and viral shedding period.
Recognize key diagnostic features that help differentiate Parvovirus B19 from other viral exanthems and systemic illnesses.
Formulate an evidence-based management plan for patients with suspected or confirmed Parvovirus B19, including those with underlying hemolytic disease or immunocompromise.
Counsel families and caregivers—including pregnant household contacts—on the risks, exposures, and infection control considerations related to Parvovirus B19.

Connect with Brad Sobolewski

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References

Jordan, Jeanne A. “Treatment and Prevention of Parvovirus B19 Infection.” UpToDate, Jun. 14, 2024. https://www.uptodate.com/contents/treatment-and-prevention-of-parvovirus-b19-infection

Edwards, Morven S. “Clinical Manifestations and Diagnosis of Parvovirus B19 Infection.” UpToDate, Jun. 14, 2024. https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-parvovirus-b19-infection

Macri, Angela, and Crane, Jonathan S. “Parvoviruses.” StatPearls, NCBI Bookshelf, Jun. 28, 2023. https://www.ncbi.nlm.nih.gov/books/NBK482245/

Kostolansky, Sean, and Waymack, James R. “Erythema Infectiosum.” StatPearls, NCBI Bookshelf, Jul. 31, 2023. https://www.ncbi.nlm.nih.gov/books/NBK513309/

“Parvovirus B19 Infection and Pregnancy.” Centers for Disease Control and Prevention. https://www.cdc.gov/parvovirusb19/pregnancy.html

Transcript

Note: This transcript was partially completed with the use of the Descript AI and the Chat GPT 4o AI

Welcome to PEMCurrents, the Pediatric Emergency Medicine Podcast. As always, I’m your host, Brad Sobolewski, and today we are covering Parvovirus B19—a common but clinically diverse viral infection that you will definitely encounter in pediatrics, and not just in the form of a rash. Parvovirus B19 is best known for causing fifth disease, but in certain patients it can lead to some serious complications like aplastic crises, fetal hydrops, or chronic anemia.

So as you can see, this virus does a lot of stuff. But what is it? Well, let’s get nerdy. It is a non-enveloped, single-stranded DNA virus in the Parvoviridae family. There are some forms of parvo that infect other mammals, but Parvovirus B19 is only for humans, and it loves erythroid progenitor cells. It was discovered by accident back in 1975, so a little bit before I was born, and it was labeled B19 because of the sample number in a Hepatitis B screening panel. Since then it has been identified as the cause of several syndromes. I’ll go over those as we move along here.

Parvovirus B19 is spread via respiratory droplets, much less commonly by blood products or vertical transmission. The incubation period is typically four to fourteen days. Viremia peaks at days five through ten after exposure, and that’s when the patient is most contagious. The classic rash and joint symptoms appear later, and at that point, the patient is actually no longer infectious. So that detail’s key—because when a kid shows up with a slapped cheeks rash, you no longer need to isolate them.

So the classic presentation that’s on every board exam ever is called erythema infectiosum, or fifth disease. This is the most well-known manifestation, seen primarily in school-aged children, especially in the spring and early summer. Again, it’s also known as fifth disease—this is one of the six classic childhood exanthems. These are a group of viral rash-causing illnesses that were originally numbered in the late 19th and early 20th centuries based on their order of description.

So: first disease was measles or rubeola, which obviously we don’t see as much anymore. Second disease was scarlet fever from group A Streptococcus. Third disease was rubella, or German measles. Fourth disease was Dukes’ disease, now believed to be a misclassified form of scarlet fever or staphylococcal scalded skin syndrome. Fifth disease is erythema infectiosum caused by Parvovirus B19. Sixth disease is roseola infantum, caused by HHV-6, and sometimes HHV-7.

Honestly, fifth disease is a historical happenstance—and I just think it’s fun to know that. Sometimes I share it with patients and families.

Here’s how it typically plays out. Phase one is the viral prodrome. This occurs during peak viremia. About 50% of symptomatic patients experience nonspecific flu-like symptoms: low-grade fever, malaise, myalgias, headache, coryza, nausea, and sometimes even diarrhea. This lasts about two to three days.

Phase two is the classic rash. This appears two to five days after the prodrome. You get an erythematous malar rash with circumoral pallor—the classic slapped cheeks appearance. You can also see a lacy, reticular rash on the trunk and extremities, which follows the slapped cheek rash about one to three days later. This rash can fade within a week or two, or it can wax and wane for weeks, especially worsening with sun, exercise, or stress. By the time the rash appears, viremia has resolved and the patient usually feels well.

Only about 25% of infected individuals will have this classic rash syndrome. Another 50% will only have mild flu-like illness, and 25% remain completely asymptomatic.

Let’s talk about the joint symptoms. These are seen in about one out of ten children. More commonly, adults—especially women—have joint symptoms, affecting up to 60% of them. Typically, joint symptoms are symmetric and affect the small joints of the hands, wrists, knees, and feet. The joint pains can last about one to three weeks. Chronic arthropathy occurs in a very small subset of patients and can last for months or more. Importantly, there’s no joint destruction—it hurts, but the joints are fine afterwards.

A serious manifestation of Parvovirus B19 infection that you do not want to miss is called transient aplastic crisis. This occurs when Parvovirus B19 halts erythropoiesis in patients with underlying hemolytic disorders like sickle cell disease, thalassemia, or hereditary spherocytosis. In one study of just over 300 patients with homozygous sickle cell disease, Parvovirus B19 infection caused transient aplastic crisis about 80% of the time.

Presenting symptoms are those of anemia: pallor, fatigue, tachycardia, weakness. You’ll often see a hemoglobin drop of greater than 30% from baseline, an undetectable reticulocyte count, and possibly leukopenia and thrombocytopenia. This often requires hospitalization and transfusion—in one series, 87% of children with transient aplastic crisis required packed red blood cell transfusions.

In immunocompromised children, B19 can also cause chronic infection, with persistent viremia and pure red cell aplasia. You’ll see this in transplant patients, patients with leukemia, or advanced HIV. These patients don’t get rash or joint symptoms—those are immune-mediated—and these kids have compromised immune systems. Diagnosis is confirmed with PCR, often as part of a viral panel, or via characteristic bone marrow findings. Treatment is with IVIG and, if possible, reduction of immunosuppression, though this can be tricky. These patients often need admission and careful care.

Let’s talk about fetal infection. Parvovirus B19 is not routinely screened for in pregnancy, but vertical transmission can cause hydrops fetalis, stillbirth, and severe fetal anemia. The risk is highest in the second trimester. The overall rate of fetal loss after maternal infection is around 2 to 6%, but it may be higher depending on timing and fetal response.

Now, let’s talk about a wonderfully named manifestation: papular purpuric gloves and socks syndrome. This is why pediatrics is great—we have the best names for things. This is a rare manifestation of Parvovirus B19, often seen in adolescents or young adults. You get painful, pruritic petechiae and purpura of the hands and feet, with a sharp demarcation at the wrists and ankles. You may also see mucosal erosions. You’re probably thinking, this sounds like mycoplasma or other viral illnesses—and it does. But unlike fifth disease, patients are contagious when this rash appears.

Finally, let’s talk about some rare neurologic complications. These include encephalitis, Guillain-Barré syndrome, and brachial plexopathy. One review identified about 129 cases of parvovirus-related neurologic complications between 1970 and 2012, with encephalitis making up about two-thirds of those cases. These are rare, but something to keep in mind—especially if you’re in a large academic children’s hospital.

So how do we diagnose Parvovirus B19? It’s usually a clinical diagnosis—especially in cases of typical erythema infectiosum. In more complicated cases or in immunocompromised children, you can check IgM antibodies (which appear about 7 to 10 days after exposure and peak at 2 to 3 weeks). IgG indicates past infection. PCR is most useful in immunocompromised patients or when evaluating possible fetal infection.

Management of erythema infectiosum is supportive care only—antipyretics, hydration, and reassurance. The rash can be itchy; use moisturizers or antihistamines like cetirizine. Explain to families that the rash may last for days to weeks and can worsen with sunlight. I’ve seen a lot of visits in urgent care where this is the main concern during outbreaks.

For joint symptoms, use NSAIDs. A patient with transient aplastic crisis will likely need hospitalization and red blood cell transfusion, especially if unstable. In immunosuppressed patients with chronic infection, treat with IVIG and carefully consider immunosuppressive management.

What if the child has a pregnant caregiver? The child is most contagious **before** the rash appears—during the viral prodrome—so it’s easy to mistake for another virus. Once the rash appears, the child is no longer infectious. If a pregnant household contact was exposed during the contagious period—especially in the first or second trimester—they should contact their OB provider for serologic testing (IgG and IgM). If seronegative, serial ultrasound may be recommended to monitor for fetal hydrops.

Isolation of the child is not necessary after the rash appears. If they are in the viremic phase, then hand hygiene and respiratory precautions are important to limit household spread.

Take-home points:
Parvovirus B19 can cause a range of presentations—from slapped cheeks to life-threatening anemia. It’s a clinical diagnosis, especially in typical cases. If you’re not familiar with the rash, look it up—so you’ll recognize it in the ED. In patients with red cell disorders or immunosuppression, use PCR or serology. Don’t miss a transient aplastic crisis in a child with sickle cell. And remember: once the rash appears, the child is no longer contagious. The virus spreads during the early, flu-like phase.

Thank you for listening to this episode. If you found it helpful, let me know. Leave a review, shoot me a message on social media or email, and share it with your colleagues and learners. And as my 13-year-old would like to remind me: like and subscribe.

For PEM Currents, this has been Brad Sobolewski. See you next time.

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