Eythema infectiosum is caused by the parvovirus B19. It involves a low-grade fever, tiredness, and a rash over the body and, notably, on the cheeks.
It is sometimes called “slapped cheek syndrome,” because the rash makes the cheeks, or “fifth disease,” as it used to be 5th among a common group of childhood diseases with similar rashes. These were measles, rubella (German measles), scarlet fever, and Dukes’ disease.
The virus can affect any age, but it mostly occurs between the ages of 5 and 14 years, and especially in children from 5 and 7 years. Most people only catch it once, and then they are immune. It is more common during the spring.
Erythema infectiosum only affects humans. Some types of parvovirus can affect animals, but humans and animals cannot catch parvovirus B19 from each other.
The effects are normally mild, but, life-threatening complications can arise. The American Osteopathic College of Dermatology (AOCD) describes it as “relatively common and mildly contagious.”
Erythema infectiosum is sometimes called slapped cheek syndrome, because a rash makes the cheeks red.
Symptoms tend to be mild. They require little or no treatment.
About one in three patients do not develop symptoms. A child can have the infection without noticing it.
The incubation period is about 13 to 18 days. At this time, the disease is contagious.
Symptoms do not usually appear at this stage, so it can spread while people do not know they have it. As soon as the rash appears, the patient is no longer contagious.
Possible early symptoms
About 10 percent of people will have cold-like symptoms for 5 to 10 days in the early stages.
Possible symptoms include:
However, this is less common.
The main symptoms
As the virus develops, the following signs and symptoms are possible:
slightly elevated body temperature
A rash appears in three stages.
A blotchy red rash may appear on the cheeks. Red papules emerge. These group together within a few hours to form red, slightly swollen, warm plaques. They do not affect the nose or mouth.
After about 4 days, a net of red marks may appear on the arms and trunk. These form into a lacy pattern.
The third stage is recurrent. It is invisible, but exposure to sunlight or heat may cause it to appear. After about 3 weeks, the rash will normally disappear, but it can last from 1 to 6 weeks.
The rash may be itchy, but it is rarely painful. As it tends to appear towards the end of the illness, it may be mistaken for a drug-related rash or another disease.
Less common symptoms are:
nausea, diarrhea, or both
arthralgia, or joint pain, normally only in adults
Adults may experience pain and soreness in their joints, especially the hands, wrists, knees, and ankles. Joint pain can last from 2 weeks to over a year.
Rarely, an adult may experience neurological or cardiovascular problems.
Causes and transmission
Parvovirus B19 is a single-stranded virus that targets red cells in the bone marrow.
The virus spreads between humans through the air, saliva, or as a result of close contact.
The most common form of transmission is through sneezing or coughing, and sometimes hand-to-hand contact.
It can spread rapidly in places where many people congregate, such as schools, kindergartens, and nurseries. Rarely, transmission may occur through blood products.
There are dog and cat versions of the virus, called canine parvovirus and feline panleukopenia virus, but parvovirus B19 only infects humans. A human cannot catch fifth disease from an animal, and an animal cannot catch it from a human.
Once the rash appears, the person is no longer contagious. They can spend time with other people and they will not transmit the disease.
Although parvovirus mostly infects elementary-aged schoolchildren during the winter and spring months, people of any age may be affected.