Fifth disease is one of the most common childhood infections. By age 20, roughly half of all adults have antibodies showing they’ve already had it, and by age 40, that number climbs above 70%. Most people catch it during elementary school years, and many never realize they were infected at all.
How Many People Get Fifth Disease
Fifth disease follows a clear age pattern. Only 2% to 9% of children under five have been infected, but that jumps to 15% to 35% among kids aged 5 to 18. Among adults 19 and older, 30% to 60% carry antibodies, meaning they were infected at some point and are now immune. The virus spreads easily in schools and daycare settings, which is why infection rates climb steeply once kids start spending time in group environments.
About 20% of people who catch the virus never develop any symptoms. In one study of household contacts of infected patients, 32% had blood markers of active infection but reported feeling completely fine. This silent spread is one reason fifth disease is so widespread: people pass it along before anyone knows they’re sick.
When Cases Peak
Fifth disease typically circulates in cycles, with small outbreaks every four to five years and a seasonal peak in late winter and early spring. Between outbreaks, the virus stays at low levels in the population. During outbreak years, classrooms and families can see clusters of cases over a few weeks.
The pattern shifted recently. In 2023 and 2024, several countries experienced unusually large and prolonged outbreaks that broke the typical seasonal mold. In France, cases peaked in July 2023 and May 2024 rather than during the expected winter-spring window. In the United States, the CDC issued a health alert in 2024 after detecting a sharp rise in recent infections across all age groups. The proportion of people showing markers of recent infection jumped from less than 3% to 10% overall, with the most dramatic spike among children aged 5 to 9, where rates went from 15% to 40%.
Why It Spreads So Easily
The timing of contagion is what makes fifth disease tricky to contain. A person is most infectious in the days before any visible symptoms appear. By the time the characteristic “slapped cheek” rash shows up on a child’s face, they are no longer contagious. This means isolating kids with the rash doesn’t actually prevent spread, because the window for transmission has already closed.
The virus travels through respiratory droplets (coughs, sneezes, close contact) and can also spread through blood. In household settings where one person is infected, secondary infection rates are high, particularly among children who haven’t been exposed before.
Who Faces the Highest Risk
For most children, fifth disease is mild. It starts with cold-like symptoms (low fever, runny nose, headache) followed by the bright red facial rash and sometimes a lacy rash on the arms and legs. The rash can come and go for a few weeks, triggered by sunlight, heat, or exercise, but the infection resolves on its own.
Adults who catch fifth disease for the first time tend to have a rougher experience. Joint pain and swelling, particularly in the hands, wrists, and knees, are common in adult cases and can last weeks or occasionally months. The facial rash is less common in adults.
Pregnant women are a particular concern. When a pregnant person is newly infected, the virus crosses to the fetus 17% to 33% of the time. Fetal infection can cause severe anemia and a dangerous buildup of fluid called hydrops fetalis, which can lead to miscarriage, particularly in the first and second trimesters. Because people are contagious before symptoms appear and one in five cases is completely silent, avoiding exposure during pregnancy is difficult. Pregnant individuals who work with young children or have school-age kids at home face the greatest exposure risk during outbreaks.
People with weakened immune systems or certain blood disorders (like sickle cell disease) can also develop serious complications, because the virus temporarily shuts down production of red blood cells. In someone whose red blood cells already break down faster than normal, this pause in production can trigger a severe anemia crisis.
What Immunity Looks Like
Once you’ve had fifth disease, you develop lifelong immunity. This is why the infection is so heavily concentrated in childhood: by the time most people reach middle age, they’ve already encountered the virus. The 70%-plus immunity rate among adults over 40 means that large outbreaks primarily affect children and the shrinking pool of adults who were never exposed.
There is no vaccine for fifth disease. Immunity comes only from natural infection. During outbreak years, the main practical concern is for pregnant women and people with compromised immune systems, since everyone else either already has immunity or will recover without complications.