CDC Health Advisory: Increase in Human Parvovirus B19 Activity

On Aug. 13, the Centers for Disease Control and Prevention (CDC) issued a Health Alert Network (HAN) Health Advisory to notify healthcare providers, public health authorities, and the public about current increases in human parvovirus B19 activity in the United States.

The alert says that “Parvovirus B19 is a seasonal respiratory virus that is transmitted through respiratory droplets by people with symptomatic or asymptomatic infection. In the first quarter of 2024, public health authorities in 14 European countries observed unusually high numbers of cases of parvovirus B19. In the United States, there is no routine surveillance for parvovirus B19, and it is not a notifiable condition. Recently, CDC has received reports indicating increased parvovirus B19 activity in the United States. Data include increased test positivity for parvovirus B19 in clinical specimens and pooled plasma from a large commercial laboratory, and reports of clusters of parvovirus B19-associated complications among pregnant people and people with sickle cell disease. The proportion of people with IgM antibodies, an indicator of recent infection, increased among all ages from <3% during 2022–2024 to 10% in June 2024; the greatest increase was observed 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 in respiratory droplets, with 50% of susceptible people infected after household exposure and 20–50% of susceptible students and staff infected during school outbreaks. Historically, people working in schools and in close contact with children have had high occupational risk of infection. About 50% of adults have detectable antibodies by age 20 years. More than 70% of adults have detectable antibodies by age 40 years. Antibodies from prior infection are thought to protect against reinfection.

Further, parvovirus B19 infection can be transmitted during pregnancy (i.e., from mother to the fetus) or through transfusion of blood components and certain plasma derivates. The Food and Drug Administration (FDA) recommends testing all plasma-derived products and plasma units for parvovirus B19 using nucleic acid tests. Whole blood is not screened for parvovirus B19 in the United States. Transfusion-associated parvovirus B19 infection is extremely rare.

The release adds that “Recently, CDC has received reports indicating increased parvovirus B19 activity in the United States. These reports include data from commercial laboratories of increasing parvovirus B19 test positivity by nucleic acid amplification tests and serology in the general population and increased serological evidence of infection in plasma donors. The proportion of people with IgM antibodies increased among all ages from <3% during 2022–2024 to 10% in June 2024; the greatest increase was observed 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. CDC has also received anecdotal reports from clinicians who have observed more than the expected number of cases of parvovirus B19 infections among pregnant people, including cases resulting in severe fetal anemia requiring fetal transfusions or pregnancy loss, and increases in aplastic anemia among people with sickle cell disease. There is no routine surveillance for parvovirus B19 in the United States.”

The alert also has several recommendations for healthcare providers including increased suspicion for parvovirus B19 among people presenting with compatible symptoms (i.e., fever, rash, arthropathy, or unexplained anemia with low reticulocyte count) and providing counseling and having a low threshold to test people who present with signs and symptoms.