Overview

Fifth disease, also known as erythema infectiosum, is a mild viral illness that primarily affects children but can also occur in adults. It is caused by parvovirus B19 and is characterized by a distinctive red rash on the cheeks, often described as a “slapped cheek” appearance. The illness is typically mild and self-limiting, resolving within a few days to a week. Fifth disease is one of the five classic childhood exanthems (rash-causing diseases), which is why it is called “fifth.” While it is generally harmless in healthy individuals, the disease can pose risks during pregnancy and for individuals with weakened immune systems or certain blood disorders.

Causes

The cause of fifth disease is infection with parvovirus B19. This virus is highly contagious and spreads from person to person through respiratory droplets when an infected person coughs or sneezes. It can also spread through:

• Direct contact: Sharing utensils or close physical contact can transmit the virus.
• Blood transmission: Rarely, the virus can spread through blood transfusions or from a pregnant mother to her unborn baby.

The disease is most contagious during the early stage before the rash appears, meaning many individuals unknowingly spread the virus before realizing they are infected.

Symptoms

Fifth disease symptoms typically develop within 4 to 14 days after exposure to parvovirus B19. The illness progresses through distinct phases:

• Initial flu-like symptoms: Mild fever, headache, fatigue, sore throat, and muscle aches may occur during the early phase.
• Facial rash: A bright red rash appears on both cheeks, giving the characteristic “slapped cheek” appearance, especially in children.
• Body rash: A lacy, pink rash may spread to the arms, legs, and trunk. This rash may fluctuate in intensity and can worsen with heat, sunlight, exercise, or stress.
• Joint pain: In adults, especially women, joint pain and swelling are common, typically affecting the hands, wrists, knees, and ankles.
• Non-contagious stage: Once the rash appears, the individual is usually no longer contagious.

Diagnosis

Diagnosis of fifth disease is usually based on clinical evaluation, particularly the characteristic rash. Additional diagnostic steps include:

• Physical examination: A healthcare provider assesses the rash pattern, timing of symptoms, and overall health condition.
• Blood tests: In certain cases, especially in pregnant women or individuals with weakened immune systems, blood tests may be ordered to detect parvovirus B19 antibodies (IgM and IgG) or viral DNA.
• Prenatal testing: Pregnant women exposed to fifth disease may undergo additional blood tests and ultrasound monitoring to assess fetal health.

Treatment

There is no specific antiviral treatment for fifth disease, as it usually resolves on its own. Treatment focuses on relieving symptoms and providing supportive care:

• Rest and hydration: Getting adequate rest and drinking plenty of fluids help the body recover.
• Pain relief: Over-the-counter medications like acetaminophen or ibuprofen can reduce fever, headaches, and joint discomfort.
• Avoiding sunlight: Since heat and sunlight can exacerbate the rash, avoiding direct exposure may help minimize irritation.
• Monitoring high-risk groups: Pregnant women, individuals with sickle cell disease, or those with weakened immunity may require close monitoring or hospitalization for complications such as anemia.

Prognosis

Fifth disease has an excellent prognosis in most healthy children and adults. The rash and associated symptoms usually resolve within 1 to 3 weeks without lasting effects. Joint pain in adults may persist for several weeks but typically resolves without permanent joint damage.

In some cases, complications can occur:

• Pregnancy: Parvovirus B19 infection during early pregnancy can rarely lead to fetal anemia or miscarriage.
• Chronic anemia: People with blood disorders like sickle cell anemia may experience severe anemia and require medical treatment.
• Immunocompromised individuals: Those with weakened immune systems may have prolonged or severe infections needing specialized care.

Overall, fifth disease remains a mild, self-limiting illness in most people, with full recovery expected in the majority of cases.