Human parvovirus B19 is a virus that infects humans, leading to a condition commonly known as fifth disease. This name originated because it was the fifth on a historical list of common viral rash illnesses in children. Human parvovirus is distinct from parvoviruses that affect animals, such as canine parvovirus, and it cannot be transmitted between pets and people. For most healthy children, fifth disease is a mild, self-limiting illness that resolves without intervention. The virus is widespread, with infections occurring more frequently during the spring months, often in localized outbreaks among school-aged children.
Symptoms of Fifth Disease
The symptoms of fifth disease appear 4 to 14 days after the initial infection and often begin with nonspecific, cold-like signs. Children may experience a low-grade fever, headache, muscle aches, or a runny nose for a few days. Following this initial phase, the most recognizable symptom emerges: a bright red rash on the face, often described as a “slapped cheek” appearance.
A few days after the facial rash appears, a second rash may develop on the chest, back, arms, and legs. This body rash often has a lacy or net-like pattern as it starts to fade and can sometimes be itchy. The rash can fluctuate, sometimes reappearing in response to heat or sunlight, and resolves within 7 to 10 days. While the rash is prominent in children, many infected individuals may have no symptoms at all.
In adults, the presentation of parvovirus B19 infection can be different and often does not include the characteristic rash. Adults, particularly women, are more likely to experience acute joint pain and swelling, a condition known as polyarthropathy syndrome. This joint discomfort affects the hands, feet, and knees symmetrically and can be mistaken for arthritis. The joint pain subsides within one to three weeks but can persist for months in some cases.
How Human Parvovirus Spreads
The primary method of transmission for human parvovirus B19 is through respiratory secretions. When an infected person coughs or sneezes, they release small droplets containing the virus, which can then be inhaled by others. This mode of spread facilitates transmission within close-contact environments like households and schools.
Beyond respiratory droplets, the virus can also be transmitted through blood or blood products, although this is less common. Another route is vertical transmission from a pregnant person to their fetus during pregnancy.
An infected person is most contagious during the initial, early phase of the illness, before the telltale rash appears. This is the period when they may only have mild, cold-like symptoms. By the time the “slapped cheek” rash and subsequent body rash are visible, the individual is no longer considered contagious. People with weakened immune systems, however, may remain contagious for a longer duration.
Specific Risks for Vulnerable Populations
While typically mild, parvovirus B19 can cause serious health complications for certain vulnerable groups. For pregnant people, an infection during the first half of pregnancy can increase the risk of miscarriage. The virus can be transmitted to the fetus, potentially leading to severe fetal anemia and a condition called hydrops fetalis, where excess fluid builds up in the fetus’s body. Most infections during pregnancy do not result in serious outcomes, but medical guidance is necessary following exposure.
Individuals with weakened immune systems, such as those with HIV, leukemia, or who have had an organ transplant, face different risks. Their bodies may struggle to clear the virus, which can lead to the development of chronic anemia. This persistent anemia can become severe and may require ongoing medical treatment to manage.
Another at-risk group includes individuals with pre-existing blood disorders like sickle cell disease or thalassemia. For these individuals, a parvovirus B19 infection can trigger a transient aplastic crisis. This is a temporary but serious event where the bone marrow stops producing red blood cells, leading to a rapid drop in blood count that requires immediate medical attention.
Diagnosis and Symptom Management
The diagnosis of fifth disease is frequently made based on its clinical presentation, especially the distinctive “slapped cheek” facial rash in children. For individuals in high-risk groups or in cases where the diagnosis is uncertain, a blood test can be performed to detect antibodies to parvovirus B19 and confirm the infection.
As fifth disease is caused by a virus, there is no specific cure or antiviral medication available for treatment. Management of the illness focuses on relieving symptoms and providing supportive care to make the individual more comfortable. This involves getting adequate rest and staying hydrated.
For managing symptoms like fever, headaches, or joint pain, over-the-counter medications such as acetaminophen or ibuprofen can be effective. It is always recommended to consult with a doctor before administering any medication to a child.