Enlarge / Child with a rash that looks like he's been “slapped on the cheek”
A common seasonal respiratory virus that infects school-age children has caused an unprecedented surge in cases in Europe and the United States this summer. The surge in infections poses a greater risk to certain vulnerable groups, including pregnant women, according to a health alert issued Tuesday by the Centers for Disease Control and Prevention.
The virus, parvovirus B19, also known as B19V, spreads by respiratory droplets and usually causes a mild, two-stage illness in children. The first stage is characterized by flu-like symptoms, including fever, headache, fatigue, muscle aches, cough, sore throat and joint pain. The second stage is characterized by a characteristic “slapped cheek” rash, also known as erythema infectiosum. By age 20, about 50 percent of people have been infected and have antibodies that help prevent reinfection. By age 40, that number rises to 70 percent.
However, for people with weakened immune systems, those who are pregnant, or those with certain illnesses such as sickle cell anemia, the virus can cause serious complications such as severe anemia, myocarditis, hepatitis, and encephalitis. During pregnancy, the virus can infect the fetus, causing dangerous complications or even miscarriage.
Typically, the virus spreads largely unnoticed and rarely causes severe illness. But in recent months, B19V has been eclipsing the din of seasonal viruses. For example, late last year, Israeli medical researchers reported the largest and longest-running B19V epidemic in the country to date. Infection rates have increased nine-fold from 2020 to 2022 and 6.6-fold compared to previous years. During the epidemic, the risk to pregnant women has increased relatively.
An international surge
In June, Danish researchers reported that the peak in infections earlier this year was the highest infection rate in the past decade, 3.5 times higher than the next highest peak, in 2017. But Denmark is not alone: Also in June, the European Centre for Disease Prevention and Control reported an unusual rise in B19V infections in 14 European countries.
According to the US CDC, although data is limited, a surge in cases in North America appears to have begun in June. Because B19V is often associated with mild symptoms, it is not a nationally reportable disease in the US, meaning cases are not tracked. However, the CDC does passively collect data on the virus.
For example, private laboratories have reported an increase in test positivity rates, and the percentage of people with IgM antibodies, an indicator of recent infection, increased from less than 3% between 2022 and 2024 to 10% in June of this year across all age groups. The largest increase was among children ages 5 to 9, from 15% between 2022 and 2024 to 40% in June 2024. Among plasma donors, the prevalence of pooled samples with threshold levels of B19V DNA increased from 1.5% in December 2023 to 20% in June 2024. The CDC also said it has received anecdotal reports of an increase in B19V cases in pregnant patients.
The CDC is urging clinicians to be more vigilant about the possibility of B19V infection. For pregnant women and others at high risk, the CDC recommends taking precautions such as wearing a mask and practicing good hand hygiene. This is especially important for high-risk individuals who work in close contact with children, such as in schools or daycare centers, the CDC noted.
The cause of B19V's spread is unknown, but researchers note that B19V tends to experience small surges every 3-4 years. The global emergence of SARS-CoV-2 in late 2019 disrupted many of the seasonal and cyclical patterns of infection, resulting in unusual declines and spikes in infections. B19V infections may have been affected in a similar way.
