Increase in Human Parvovirus B19 Activity in the United States

 

 Health Alert Notification: Increase in Parvovirus B19 Activity in the U.S.

**Issued by: The Centers for Disease Control and Prevention (CDC)**

The CDC is issuing this Health Alert Network (HAN) Health Advisory to inform healthcare providers, public health authorities, and the public about the current increase in human parvovirus B19 activity in the United States. Parvovirus B19 is a seasonal respiratory virus transmitted through respiratory droplets by individuals with symptomatic or asymptomatic infections. 

- **Europe:** In the first quarter of 2024, 14 European countries reported unusually high numbers of parvovirus B19 cases.

- **United States:** There is no routine surveillance for parvovirus B19, and it is not a notifiable condition. However, the CDC has received reports indicating increased activity in the U.S., including:

  - Increased test positivity for parvovirus B19 in clinical specimens and pooled plasma from a large commercial laboratory.

  - Reports of clusters of parvovirus B19-associated complications among pregnant individuals and people with sickle cell disease.

  - The proportion of people with IgM antibodies (an indicator of recent infection) increased from <3% during 2022–2024 to 10% in June 2024, with the greatest increase among children aged 5–9 years (from 15% during 2022–2024 to 40% in June 2024).

  - Among plasma donors, the prevalence of pooled samples with parvovirus B19 DNA >104 IU/mL increased from 1.5% in December 2023 to 19.9% in June 2024.

Parvovirus B19 is highly transmissible through respiratory droplets:

- **Household Exposure:** 50% of susceptible individuals become infected.

- **School Outbreaks:** 20–50% of susceptible students and staff may be infected.

- **Occupational Risk:** High risk for those working closely with children, such as daycare workers and teachers.

**Antibodies:**

- 50% of adults have detectable antibodies by age 20.

- Over 70% of adults have detectable antibodies by age 40.

- Prior infection antibodies are believed to protect against reinfection.

**Transmission:**

- During pregnancy (from mother to fetus).

- Through transfusion of blood components and certain plasma derivatives.

- The FDA recommends testing all plasma-derived products for parvovirus B19 using nucleic acid tests, but whole blood is not screened in the U.S.

- Transfusion-associated parvovirus B19 infection is extremely rare.

**Symptoms and Illness Progression:**

- **Asymptomatic:** Many people with parvovirus B19 infection are asymptomatic.

- **Symptomatic Disease:** Immunocompetent children and adults typically develop a biphasic illness.

  - **First Phase:** Symptoms include fever, myalgia, and malaise, appearing approximately 7 days post-infection and lasting about 5 days. Most contagious during this phase.

  - **Second Phase:** 

    - Children often develop a characteristic facial rash (erythema infectiosum or "slapped cheek" appearance), followed by a reticulated body rash or joint pain.

    - Adults typically experience a reticular rash on the trunk and joint pain. The facial rash appears after viral loads have declined.

  - **Laboratory Tests:** During acute illness, transient decreases in absolute reticulocyte counts, mild anemia, thrombocytopenia, or leukopenia may occur.

  - **Severe Outcomes:** Rarely, severe outcomes like myocarditis, hepatitis, or encephalitis may occur. No vaccine or specific treatment is recommended for parvovirus B19 infection.

**High-Risk Populations:**

- **Pregnant Individuals:** Increased risk of adverse fetal outcomes, such as fetal anemia, non-immune hydrops, or fetal loss, especially when acute infection occurs between gestational weeks 9–20. Treatment involves supportive care and monitoring for severe fetal anemia.

- **Immunocompromised Individuals:** Those with leukemia, other cancers, organ transplants, HIV infection, or receiving chemotherapy are at risk for chronic or transient aplastic anemia. 

- **People with Chronic Hemolytic Disorders:** Individuals with sickle cell disease, thalassemia, or hereditary spherocytosis may require red blood cell transfusions and intravenous immunoglobulin for treatment.

### Recommendations for Healthcare Providers

1. **Increased Vigilance:** Be alert for parvovirus B19 in patients presenting with compatible symptoms (fever, rash, arthropathy, or unexplained anemia with low reticulocyte count).

2. **Preventive Counseling and Testing:** 

   - Test individuals at higher risk of severe parvovirus B19 disease, including:

     - Pregnant individuals.

     - Those with severely immunocompromising conditions.

     - Individuals with chronic hemolytic blood disorders.

   - Inform patients or caregivers about high-risk groups and advise exposed contacts to consult healthcare providers.

3. **Standard Care:** Follow professional guidelines for testing pregnant individuals exposed to parvovirus B19 or presenting with compatible symptoms.

4. **Preventive Measures:** Promote CDC recommendations for respiratory illness prevention, including good hand hygiene and measures for cleaner air.

5. **Workplace Precautions:** High-risk individuals working in high-exposure settings should practice hand hygiene, avoid sharing food or drinks, and consider wearing masks. No proven benefit to removing individuals from such work settings.

6. **Infection Control:** Follow recommended precautions for individuals with parvovirus B19 in healthcare settings.

For further information and updates, visit the CDC website.