• The CDC issued an alert over rising human parvovirus B19 cases, also known as “fifth disease” and “slapped-cheek disease.”
• Most cases are generally mild and occur in children, leading to a fever and trademark bumpy red rash on the face or elsewhere on the body.
• Pregnant people and immunocompromised individuals face the highest risk of parvovirus-related complications.
• Currently, there is no vaccine against this infectious disease.

A highly transmissible virus you may have never heard of is circulating as summer draws to a close.

The Centers for Disease Control and Prevention (CDC) recently received reports of human parvovirus B19 activity among people of all ages in the United States, notably children.

Clusters of parvovirus-related complications among pregnant people and people with sickle cell disease were also identified.

“In the first quarter of 2024, public health authorities in 14 European countries observed unusually high numbers of cases of parvovirus B19,” a CDC health adivsory reported on August 13. “In the United States, there is no routine surveillance for parvovirus B19, and it is not a notifiable condition.”

The CDC’s alert advises healthcare professionals to screen high risk patients presenting associated symptoms, which include fever and unexplained anemia, and the trademark rash that gave this disease its “slapped cheek” nickname.

Children who contract parvovirus are more likely to develop a bumpy red rash on their cheeks, whereas adults may develop a rash elsewhere on the body.

Most healthy adults and children are considered low risk for serious illness from this respiratory disease, which is often asymptomatic, and will not require treatment.

“Because Parvovirus B-19 is mostly contagious before symptoms present or in the early stages, the only recommendation is to stay home if [you have a fever],” Jennifer Walsh, assistant professor at George Washington University School of Nursing, told Healthline. “Once the typical childhood rash presents, the individual is no longer considered contagious.”

Other groups, such as immunocompromised adults and pregnant people, face higher risks of parvovirus-related complications. Here’s what you need to know to protect yourself.

How common is parvovirus?

Cases of human parvovirus B19 are increasing among people of all ages, from less than 3% in 2022–2024 to 10% in June 2024.

According to the CDC, the largest increase occurred in children ages 5–9 years, from 15% in 2022–2024 to 40% in June 2024.

Parvovirus was also detected in plasma donors 19.9% of plasma donors in June, up from 1.5% in 2023.

While the Food and Drug Administration (FDA) is required to screen donated plasma for parvovirus B19, transmission through plasma transfusions is rare in the U.S., the CDC notes.

Why is it called the ‘slapped cheek’ disease?

Parvovirus (Erythema infectiosum) is transmitted through respiratory droplets and may cause a distinct, red, splotchy rash on the cheeks or other parts of the body.

Also known as “fifth disease,” parvovirus was once listed as fifth among the six common rash-related illnesses in children: measles, rubella, chicken pox, roseola, and Duke’s disease.

According to the CDC, about half of parvovirus infections occur from household exposure, with 20–50% of infections occurring at school or child care settings.

Parvovirus is considered a seasonal disease, but unlike other seasonal respiratory viruses, such as the flu, it does not occur regularly or yearly.

Because parvovirus transmission is so common among children, around half of adults have antibodies from prior infection by their 20s, with over 70% having antibodies by the time they reach 40 years of age, the CDC notes.

In many cases, people with parvovirus infection are asymptomatic. Symptoms are generally mild and should resolve within a week. These include:

• rash
• fever
• anemia
• muscle or joint pain
• swelling
• diarrhea
• malaise

Still, immunocompromised people and adults with certain health conditions may face higher risks of more severe illness.

Pregnant people at high risk for complications

Pregnant people are considered at high risk for serious complications from parvovirus.

The virus can cross the placenta and infect a developing fetus, which may cause complications such as fetal anemia, abnormal fluid buildup, or fetal loss.

“The major unfortunate aspect of this virus is, if it infects susceptible persons who are pregnant, it can have an adverse effect on them and the fetus that they’re carrying — it can lead to miscarriage,” said William Schaffner, MD, professor of preventive medicine and infectious diseases in the Department of Health Policy at Vanderbilt University Medical Center in Nashville.

“If the fetus survives, the virus can get through the placenta into the baby and cause anemia and liver disease. As you can imagine, that causes a great deal of concern on the part of the parents,” Schaffner told Healthline.

Schaffner said because there is no vaccine against parvovirus, it’s important for healthcare professionals like OB-GYNs to be aware of the current surge in cases.

According to the CDC, most cases of fetal parvovirus infection resolve without adverse outcomes. Still, there’s a 5–10% risk of an adverse fetal outcome. This risk is highest when infection occurs during weeks 9–20 of pregnancy.

For instance, a pregnant woman almost lost her baby at 18 weeks from parvovirus-related anemia, NBC recently reported.

“If people become ill, we can provide them supportive care and reassurance and insights into what is likely to happen,” Schaffner said.

Walsh noted that higher-risk populations “should contact their provider if they believe they have been exposed or suspect they have Parvovirus B-19 to discuss potential testing and management.”

Immunocompromised people are also at risk

In people who are severely immunocompromised, the CDC warns that parvovirus B19 can cause chronic or transient aplastic anemia, which can be life threatening.

Health conditions or statuses that put people most at risk for serious complications from parvovirus include:

• leukemia or other cancers
• chemotherapy
• organ transplant
• HIV
• chronic hemolytic disorders (i.e., sickle cell disease, thalassemia, hereditary spherocytosis)

Aplastic anemia is usually treated with red blood cell transfusions and intravenous immunoglobulin.

Why isn’t there a vaccine for parvovirus?

Vaccines against other common respiratory illnesses like the flu or COVID-19 do not offer immunity against parvovirus B19.

With parvovirus outbreaks being as unpredictable as they are, why haven’t researchers developed a vaccine?

According to Schaffner, it is likely because parvovirus is not considered a deadly disease.

He explained that some preliminary research has been done into developing a parvovirus vaccine, but further development may have slowed due to a lack of public awareness about the virus and ongoing vaccine hesitancy.

“We are in the midst of a great period of vaccine reluctance, hesitancy, and skepticism, and so introducing a vaccine against some weird virus that nobody’s ever heard of probably wouldn’t go over very well,” Schaffner said.

Increased awareness, further evaluation, and general acceptance of a parvovirus vaccine could lead to additional studies and clinical trials that could reduce the frequency and impact of parvovirus outbreaks, he noted.

Takeaway

The human parvovirus B19, also known as “fifth disease” or “slapped-cheek disease,” is circulating in the U.S.

The CDC received reports of a surge in parvovirus cases, most notably in children, which usually presents as a red rash on the face or other parts of the body.

Most cases of parvovirus are mild, but pregnant people and immunocompromised people face higher risks of serious complications.