CDC Issues Alert on Rising Parvovirus B19 Cases

The CDC's Health Alert issued on August 15, 2024, highlights increased human parvovirus B19 activity in the United States. This virus, typically a seasonal respiratory pathogen, has shown an unusual rise in cases, following similar trends observed earlier in 2024 across 14 European countries.¹

In an interview with Contagion, David Diemert, BMS, MD, a professor of medicine and a secondary professor of microbiology, immunology, and tropical medicine at the George Washington University School of Medicine and Health Sciences, discusses factors contributing to the recent surge in parvovirus B19 infections. He notes, "One of the main hypothesized reasons for the recent surge in parvovirus B19 infections in the US and Europe is that precautions taken during the COVID-19 pandemic (eg, masking, social distancing) led to a reduction in cases starting in 2019, which resulted in lower herd immunity to the infection. The recent surge in infections in 2024 has been higher than in pre-COVID-19 years potentially due to the lower population-level immunity that occurred due to precautions taken during the COVID-19 pandemic."

CDC reports indicate a notable surge in cases, with rising test positivity rates and increased antibody prevalence in clinical specimens and plasma samples. Specifically, the proportion of individuals with IgM antibodies, which indicate recent infection, increased from less than 3% in 2022–2024 to 10% by June 2024. Among children aged 5–9 years, infection rates surged from 15% to 40% in the same period. Additionally, among plasma donors, the prevalence of parvovirus B19 DNA increased from 1.5% in December 2023 to 19.9% in June 2024. There have also been anecdotal reports of severe outcomes, such as fetal anemia and increased aplastic anemia in individuals with sickle cell disease.²

While the FDA recommends testing plasma-derived products for parvovirus B19, whole blood is not routinely screened in the US. Healthcare providers are advised to maintain heightened suspicion of parvovirus B19 in individuals presenting with symptoms, particularly those at high risk. Preventive measures should be implemented, and counseling provided to at-risk groups. Providers should follow established guidelines for testing and managing parvovirus B19 cases. Health departments are urged to inform healthcare providers about the increase in parvovirus B19 activity and promote respiratory illness prevention strategies. They should also communicate with daycare and school providers about parvovirus B19 risks and return-to-school guidelines.²

For the public, it is important to be aware of parvovirus B19 symptoms and seek medical care if pregnant. Diemert adds, "due to the potential negative impact on a developing fetus." Also, immunocompromised, or have a chronic hemolytic disorder with signs of the virus. Good respiratory hygiene should be practiced, with additional precautions considered for those at higher risk of severe outcomes. Individuals with parvovirus B19 are no longer contagious once the characteristic rash appears.²

Diemert offers insights into how public health and clinical practices are adapting to the increased prevalence of parvovirus B19. He notes, "The main public health and clinical practice intervention is informing the public and patients about the increase in cases and to advise people at high risk to take precautions to reduce risk of infection (wearing a mask, avoiding crowded public spaces, washing hands, etc.) and to seek medical care if they develop compatible symptoms or come into contact with someone who has or is suspected of having parvovirus B19."

What is Parvovirus B19?

It is a virus that typically causes mild illness, especially in healthy individuals. It is known for causing a distinctive "slapped cheek" rash in children, also called Fifth Disease or Erythema Infectiosum. Other common symptoms include flu-like symptoms and joint pain, particularly in adults.³

The international spread suggests a potential shift in the virus's transmission or behavior. This is particularly significant as parvovirus B19 can cause various illnesses, including erythema infectiosum (fifth disease) in children, and more severe complications in adults, particularly pregnant women and individuals with weakened immune systems.¹

While the infection is usually not serious, it can cause complications in people with certain blood disorders, weakened immune systems, or during pregnancy, where it may lead to anemia or increase the risk of miscarriage. Most people recover without needing special treatment, though supportive care may be necessary for those with complications.³

This alert is important because, in the US, there is no routine surveillance for parvovirus B19, so the true extent of the outbreak may be underreported. The CDC is targeting clinical laboratory professionals to increase vigilance, testing, and reporting to manage this public health threat. The advisory highlights the need for awareness and preparedness to address the virus's impact.¹ Additional research and data collection efforts are needed to understand the implications of the increase in parvovirus B19 cases and to improve responses to future outbreaks.

"Since parvovirus B19 is not a reportable infection (ie, cases do not have to be reported to the local Department of Health), there is no ongoing comprehensive collection of data on rates of infection or complications. It would be very helpful for there to be a prospective study that enrolls people of all ages and follows them over time to get a more accurate picture of the true rate of infection (both symptomatic and asymptomatic), the types of symptoms being seen, and any complications of infection," Diemert concludes.

References

1. 08/15/2024: Lab Advisory: CDC Issues Alert for Increase in Human Parvovirus B19 Activity in the United States. CDC. August 15, 2024. Accessed August 22, 2024. https://www.cdc.gov/locs/2024/08-15-2024-Lab-Advisory_CDC_Issues_Alert_Increase_Human_Parvovirus_B19_Activity_United_States.html

2. Increase in Human Parvovirus B19 Activity in the United States. CDC. August 21, 2024. Accessed August 22, 2024. https://emergency.cdc.gov/han/2024/han00514.asp

3. About Parvovirus B19. CDC. August 13, 2024. Accessed August 22, 2024. https://www.cdc.gov/parvovirus-b19/about/index.html