Human parvovirus B19 usually causes no symptoms or a mild illness in healthy children and adults who aren't pregnant. But infection during pregnancy — especially before 20 weeks — can seriously harm the fetus. In 2024, Minnesota saw a rise.
Parvovirus B19 testing and positivity in Minnesota, from January 2019. Image from CDC's report
The alert
In July 2024, a maternal-fetal medicine specialist told the Minnesota Department of Health (MDH) about more B19 infections among pregnant patients, with fetal complications. No U.S. increase had been described, but European surveillance had shown rises in late 2023 and 2024.
Five patients
Five women aged 20–40, evaluated May–August 2024, were reported. They lived in different communities with no links between them. Four had children at home — two with sick children (one with B19 anemia needing a transfusion), and one who said B19 was going around her child's school; the fifth worked at a child care center where rash-and-fever illnesses were spreading.
All were infected at 13–20 weeks of pregnancy, confirmed by immunoglobulin M or PCR tests (three by PCR of amniotic fluid); three had symptoms such as fever, rash, fatigue, joint pain and swollen lymph nodes. None had immune or blood disorders.
| Patient | Outcome |
|---|---|
| A | fetal hydrops; the fetus died at 20 weeks, before a transfusion could be given |
| B | checked weekly for 3 months; no complications |
| C, D | severe fetal anemia needing a fetal transfusion |
| E | severe fetal anemia with hydrops (severe swelling) needing two fetal transfusions |
Patients B–E delivered full-term babies with no complications identified. Genome sequencing of two samples found the common genotype 1A but unrelated viruses, differing by at least 35 single-nucleotide changes.
A statewide picture
B19 isn't notifiable nationally or reportable in Minnesota, so there's no routine surveillance. Researchers therefore analyzed electronic health records from 10 health systems (January 2019–September 2024):
- Testing, positive tests, percent positive and diagnoses all rose in 2024, most of all among children.
- January–September 2024: 19 B19-related pregnancy complications (within 60 days of a B19 diagnosis or positive test) — hydrops, fetal anemia and low platelets, fetal transfusion or stillbirth.
- All of 2019–2023 (60 months): 28.
- Fetal complications not linked to B19 did not increase.
What to do
MDH and CDC issued health advisories.
- Patients with B19 should tell exposed contacts who are pregnant, immunosuppressed or have chronic hemolytic blood disorders, and urge them to see their providers.
- Obstetric providers should keep B19 in mind and test (serology and PCR) pregnant patients who've been exposed or have signs of maternal or fetal infection.
- Pregnant patients with B19 should be evaluated by an obstetric specialist for fetal and pregnancy complications.
- Public health should raise awareness, including among child care and schools, about who is at risk and when infected children and staff can return.
Sources
Based on Stephen Contag, Elizabeth M. Dufort, Sarah Lim and others, "Notes from the Field: Human Parvovirus B19 Infections Among Pregnant Persons — Minnesota, January–September 2024," MMWR, volume 73, Centers for Disease Control and Prevention; a work of the United States government in the public domain. The report calls January–September 2024 a 10-month period; the dates are given here instead.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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