Parvovirus B19 — the “slap in the cheek” virus — on the rise in the U.S.: NPR

Federal health officials are warning doctors to remain vigilant against the respiratory virus known as parvovirus B19 as infection rates rise in the United States.

Parvovirus B19 has been around for decades and usually causes mild or no symptoms in children and healthy adults, but can cause serious complications during pregnancy and in people with compromised immune systems and certain blood disorders.

In a health advisory issued this week, the Centers for Disease Control reported that the percentage of people testing positive for antibodies – indicating recent infection – is rapidly increasing, especially among children ages 5 to 9.

Public health officials in 14 European countries have also reported observing unusually high numbers of cases this year, according to the CDC.

Infections typically spike in the late winter, spring and early summer, with smaller outbreaks occurring every three to four years. This year, the virus has been spreading as the new school year begins.

Here’s what you need to know about the virus:

How does it spread, and how do you know if you have it?

Parvovirus B19 can be transmitted from person to person in three ways: through respiratory droplets, blood, or from a pregnant mother to her fetus. (The canine parvovirus that infects dogs is different from parvovirus B19, and it cannot be transmitted from pets to people or vice versa.)

Most people infected with parvovirus B19 are asymptomatic. If symptoms do appear, they vary by age.

In children, the disease first causes flu-like symptoms, including fever, headache, and cough. This is when children are most contagious, and symptoms usually last for a few days, according to the CDC. After that, children may develop a rash on their face, which is why the disease caused by the virus is sometimes called “slap cheek disease.”

In adults, the most common symptom is joint pain, which can last from a few days to a few weeks.

How worried should you be?

Most people recover naturally without treatment. The risk is when parvovirus B19 affects the blood flow, causing complications such as a significant drop in blood cell counts.

Parvovirus B19 infection does not usually affect the pregnancy or the fetus, but in rare cases, the infection can cause fetal anemia and miscarriage.

It’s especially dangerous for fetuses under 20 weeks into a pregnancy, but it’s treatable if caught early, said Katherine Brighardt, a Washington University obstetrician-gynecologist at Barnes-Jewish Hospital in St. Louis who has seen a surge in cases in the past few months.

“Fortunately, in the cases I have seen, we have been able to detect fetal anemia early and treat the anemia with fetal blood transfusions. All of these fetuses have either already been delivered or are still thriving in their mothers’ uteruses,” she said.

Infections can also cause severe anemia in people with weakened immune systems, such as leukemia or organ transplant patients, or in people with certain blood disorders, such as sickle cell disease or thalassemia.

Most adults have built-in immune defenses: About 50% of adults have detectable antibodies by age 20, and more than 70% of adults have detectable antibodies by age 40, according to the CDC.

How can I stay safe?

As with other respiratory viruses, the CDC recommends practicing good hygiene habits: washing your hands frequently and keeping commonly touched surfaces clean.

People at high risk of infection should also let their doctor know if they’ve been in contact with a child who has a high fever followed by a facial rash, said Dr. Kawthar Talaat, an infectious disease expert at the Johns Hopkins Bloomberg School of Public Health.

“The important thing is not to panic. This is something that most people will get without any issues,” Talaat said. “This is just a warning to let health care workers know that there are more cases this summer and to alert people who are at high risk.”

NPR’s Pien Huang contributed to this report.