Parvovirus B19 Stayed High Into 2025: What It Means for Pregnant Women

Parvovirus B19 is a respiratory virus, spread through the air by people with or without symptoms. Most people get only a mild illness, but B19 can harm a fetus when a pregnant woman is infected, and can cause severe disease in people who are immunocompromised or have chronic hemolytic blood disorders. There is no antiviral to treat it.

B19 usually peaks from April to June. After low levels during the COVID-19 pandemic years of 2021–2023, activity in 2024 rose above pre-pandemic levels, and CDC issued a Health Advisory in August 2024. Did the surge continue into 2025?

What the lab data showed

CDC's National Syndromic Surveillance Program tracked tests for B19 IgM antibodies — a sign of recent infection — run by a large commercial laboratory, from January 2023 to May 10, 2025.

Share of B19 antibody tests that were positive by week, and 2025-versus-2024 ratios by age. Image from CDC's report

Testing volume barely changed — about 1,401 tests a week in 2025 against 1,328 in 2024 — so the rise wasn't just more testing.

Compared with 2024, positivity in 2025 was significantly higher:

In the first quarter, every age group except children under 5 was significantly higher; in the second, ages 10–14 and 15–44 — which includes women of reproductive age — stayed significantly higher. Among ages 15–44, 93% of tests were ordered for females.

The numbers likely undercount infections: they include only people a clinician chose to test, and mild infections are far more common than the data show.

What doctors and patients can do

Finding B19 early allows severe anemia to be caught and treated, which can prevent harm to a fetus and serious illness in high-risk people. So health care providers should consider testing:

1. pregnant women who may have been exposed to B19, and
2. people at higher risk of severe disease who have fever, rash, joint problems or unexplained anemia with a low reticulocyte count.

Providers caring for pregnant patients should watch for reduced fetal movement or signs of hydrops, which could be linked to B19. Pregnant women and others at higher risk may want to add precautions, such as wearing a mask around other people.

Sources

Based on Alfonso C. Hernandez-Romieu, Kelly Carey, Stephanie Dietz, Aaron Kite-Powell, Olivia Almendares and Hannah L. Kirking, "Notes from the Field: Parvovirus B19 Activity — United States, January 2024–May 2025," MMWR, volume 74, Centers for Disease Control and Prevention; a work of the United States government in the public domain.