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.”
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
- flu-like symptoms
- runny nose
- stuffy nose
- sore throat
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
- abdominal pain
- 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.
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.
Signs and symptoms of erythema infectiosum tend to be easy to detect, so diagnosis is normally straightforward. It is sometimes confused with scarlet fever, but the rash is different.
Tests to confirm the presence of the virus are not generally ordered.
Around 50 percent of all adults are immune to parvovirus infections, probably because they experienced infection during childhood, even if it went unnoticed.
Sometimes a doctor may recommend a blood test to check for antibodies.
This may happen if the patient:
- is pregnant
- has a compromised immune system, due, for example, to HIV or AIDS
- has a chronic red blood cell disorder, such as sickle-cell anemia
Depending on the result, the following actions are possible:
Results show the patient is immune: no further action is required, as reinfection is not possible.
Results show a recent parvovirus infection: further tests may be ordered to find out whether any complications, for example, anemia, require treatment.
Results show a pregnant woman is infected: additional tests, including an ultrasound scan and further blood tests, will monitor the developing fetus for complications
In most cases, no treatment is required, but medications can help reduce symptoms.
The rash: treatment is not usually necessary.
Pruritis: antihistamines may help if there is severe itching of the skin.
Headache, fevers, and cold-like symptoms: the doctor may suggest Tylenol (paracetamol) or ibuprofen. Younger children can take painkillers in liquid form. It is important to check dosages and frequency of use with a qualified pharmacist, a doctor, or by reading the public information leaflet (PIL) in the package.
Joint pains and swelling: the doctor may advise rest and prescribe an anti-inflammatory drug, such as ibuprofen. In most cases, there are no long-term consequences, and the pain resolves within a few days or weeks.
Drink and rest: drinking plenty of fluids, especially water, and getting enough rest can ease symptoms and speed up recovery.
Severe anemia: this may require hospitalization and a blood transfusion.
Weakened immune system: patients may be hospitalized and antibodies provided through a blood transfusion.
Pregnancy: the doctor will carefully monitor the fetus. If there are signs of anemia, CHF, or edema, blood transfusions may be given. This will reduce the risk of miscarriage.
Most people will not experience complications. However, Parvovirus B19 can cause problems with red blood cell production, and this can impact some patients.
Pregnancy: the fetus may be at risk if a pregnant woman has fifth disease.
If a pregnant woman becomes infected, there is a slight risk that it may affect the developing fetus and a small risk of miscarriage. The risk of fetal death is between 2 and 6 percent.
However, the risk of infection during pregnancy is very small, and the risk of complications for the fetus are smaller still.
There is a 1 in 3 chance of a woman getting fifth disease during pregnancy, and, among those who get it, an estimated 3 percent chance of fetal complications.
One possible complication is fetal hydrops, which can lead to congestive heart failure (CHF) and a severe form of edema due to severe anemia.
Blood abnormalities, such as sickle-cell anemia: infection with parvovirus B19 can result in acute, severe anemia in children with hereditary anemia.
Weakened immune system: organ transplant recipients and those with diseases such as HIV or AIDS have a higher risk of developing bone marrow problems, leading to chronic anemia.
Arthritis: joint pain may affect the small joints of the hands and feet, especially in teens adults, but also in 8 percent of younger children. Symptoms can resemble those of rheumatoid arthritis. Symptoms rarely continue for more than a few weeks or months, and long-term damage is rare.
There is currently no vaccine which protects people from parvovirus B19 infection. Those who have been infected are immune and cannot be infected again.
Good hand hygiene helps stem the spread of infection.