Fifth disease is a common, usually mild viral infection caused by parvovirus B19. It’s best known for producing a bright red rash on both cheeks, often called a “slapped cheek” rash, and it primarily affects children between ages 5 and 15. The name comes from its place on a historical list of six childhood rash illnesses. Most cases resolve on their own without treatment.
How the Infection Progresses
After exposure to the virus, symptoms typically appear within 4 to 14 days. The illness unfolds in two distinct phases, which is one reason it often catches parents off guard.
The first phase looks like any ordinary cold: low fever, headache, runny nose, sore throat, and general fatigue. At this point, nothing about it suggests fifth disease. A few days after these flu-like symptoms begin to fade, the second phase kicks in with the hallmark bright red rash across both cheeks. The rash can then spread to the arms, torso, and legs in a lacy, net-like pattern. In some children, the body rash comes and goes over one to three weeks, sometimes flaring up with sun exposure, warm baths, or exercise.
Some children skip one phase entirely. They may develop the rash without ever feeling sick beforehand, or they may have the cold-like symptoms and never get a visible rash at all.
When It’s Contagious
The tricky thing about fifth disease is that a child is most contagious during the early cold-like phase, before anyone knows it’s fifth disease. The virus spreads through respiratory droplets from coughs and sneezes, and also through direct contact with contaminated surfaces.
By the time the telltale rash appears, the child is generally no longer contagious. That means it’s usually safe to return to school or daycare once the rash shows up. The exception is children with weakened immune systems or those who develop anemia from the infection, who may remain contagious for a longer period.
How It Looks Different in Adults
Adults can absolutely catch fifth disease, and when they do, the experience is often different from what children go through. The facial rash is less common in adults. Instead, the dominant symptom tends to be joint pain, particularly in the wrists, hands, and knees. About 80% of infected adults develop these flu-like symptoms along with noticeable joint stiffness and swelling.
For most adults, the joint pain resolves within a few weeks. However, roughly 10% go on to develop chronic joint inflammation affecting multiple joints, a condition called polyarthritis, which can persist for months or occasionally longer. This is one reason adults sometimes don’t realize they had fifth disease. They assume they’re dealing with a new joint problem rather than the aftermath of a viral infection.
Risks During Pregnancy
Fifth disease poses a real concern for pregnant women, particularly during the first 20 weeks. The virus can cross the placenta and interfere with the developing baby’s ability to produce red blood cells, potentially causing severe anemia in the fetus.
A large study from the United Kingdom tracked 174 pregnant women with confirmed parvovirus B19 infection. Among those infected during the first 12 weeks of pregnancy, fetal loss occurred in about 19%. For infections between weeks 13 and 20, the rate was roughly 15%. After 20 weeks, the risk dropped considerably. When researchers accounted for which fetal losses were directly caused by the virus rather than coincidental, they estimated the attributable risk at under 10%.
For a pregnant woman who has simply been in the same room as someone with fifth disease but doesn’t know her own immune status, the overall risk of fetal death is much lower, estimated at less than 2.5% for household exposure and less than 1.5% for school or workplace exposure. Many adults already carry immunity from a childhood infection they may not remember having. A blood test can confirm whether you have protective antibodies.
People With Blood Disorders
Parvovirus B19 specifically targets immature red blood cells in the bone marrow. In healthy people, this temporary disruption barely matters because red blood cells live about 120 days, and production bounces back quickly. But for people with conditions like sickle cell disease or other chronic anemias, where red blood cells already break down faster than normal, even a brief pause in production can trigger a dangerous drop in blood counts known as an aplastic crisis. This requires prompt medical attention and sometimes blood transfusions.
People with weakened immune systems face a similar concern. Their bodies may struggle to clear the virus efficiently, leading to prolonged infection and persistent anemia rather than the quick, self-limiting course most people experience.
Diagnosis
Most of the time, a doctor can diagnose fifth disease just by looking at the rash. The slapped cheek appearance is distinctive enough that no testing is needed for a typical case in a child.
When confirmation matters, such as during pregnancy or in someone with a blood disorder, a blood test can detect specific antibodies. The presence of IgM antibodies indicates a recent or active infection. If only IgG antibodies are found, it means the person was infected at some point in the past and now has immunity. Both types of antibodies can be present at the same time shortly after illness begins, with levels peaking within about 30 days. IgG antibodies persist for years, which is why a single positive IgG result alone doesn’t mean you’re currently sick.
Treatment and Recovery
There is no antiviral medication for fifth disease, and for most people, none is needed. The infection runs its course in one to three weeks. Treatment focuses entirely on comfort: rest, fluids, and over-the-counter pain relievers for fever or joint discomfort.
The rash itself doesn’t need treatment. It isn’t painful or dangerous, just visually striking. If it itches, cool compresses or an antihistamine can help. Because the rash can reappear with heat or physical activity for several weeks after the initial illness, some parents mistakenly think the infection has returned. It hasn’t. The recurring rash is just a lingering immune response.
There is no vaccine for parvovirus B19. Standard hygiene practices, frequent handwashing and covering coughs, are the main ways to reduce transmission. Since children are most contagious before anyone realizes what they have, outbreaks in schools and daycares are difficult to prevent. Excluding children after the rash appears has little effect, because by that point the contagious window has already passed.