Alternative names: Erythema infectiosum, “slapped cheek” syndrome.
Fifth disease is a relatively mild illness caused by a virus infection.
It’s called “fifth disease” because it’s the fifth of the five infectious diseases of childhood that has a typical rash. The other four illnesses are measles, rubella (German measles), chicken pox and roseola.
Fifth disease is one of several illnesses caused by infection with a virus known as human parvovirus B19.
Another name for fifth disease is “slapped cheek” syndrome. This refers to the very distinctive red rash that appears on the face of children with this illness.
After a few days, the rash changes to a typical pinkish, “lacy” appearance and spreads to the child’s body, as well as the arms and legs.
This illness is most common in children aged 5 to 15 years. Adults can also be affected, but this is rare. The illness usually lasts for about a week, but sometimes it may last for as long as three weeks.
In older children and adults, fifth disease can cause joint pain and swelling that can last for several weeks to months.
Who gets fifth disease?
Fifth disease is far more common in children than in adults.
The disease occurs worldwide and epidemics are common. The human parvovirus B19 can infect people of all ages, regions and social groups, but the clinical presentation varies depending on age, immune status and the presence of underlying diseases.
Infection occurs mainly during the winter and spring, and most commonly affects children between the ages of 5 and 15 years.
The human parvovirus B19 is mainly spread by airborne droplet infection transmitted by children who may cough or sneeze in the early stages of the illness, before the rash appears. The virus can cross the placenta and may affect the unborn child if a pregnant woman becomes infected with it.
Cases of fifth disease can occur either as individual infections or as part of community outbreaks. Outbreaks of the illness mainly occur in nursery schools, and in children in the early grades at school.
Many cases occur from the spread of the illness to others in the infected person’s home. Most adults were infected with the virus at some stage during their childhood and are unlikely to become re-infected.
People with this illness are infectious before the onset of symptoms. They’re considered to be non-infectious once the rash first appears. The incubation period, which is the time from acquiring the infection until the symptoms occur, usually lasts from 4 to 21 days.
After recovery from fifth disease, life-long immunity is usually guaranteed.
Symptoms of fifth disease
After the incubation period of 4 to 21 days, the first signs of fifth disease appear.
Typically, a rash that is bright red in colour, and which affects both of the child’s cheeks, appears (see picture below).
This rash gives the appearance that the child’s cheeks have been slapped, hence the name “slapped cheek” syndrome. Sometimes there may be only a blotchy redness on the cheeks. The rash itself is painless but may be itchy.
Usually about 1 to 3 days after the bright-red rash has appeared on the child’s cheeks, the rash changes and becomes more widespread. Now a faint “lacy” rash appears on the body, arms and legs (see picture below).
Occasionally, the rash on the cheeks and body keeps on fading and returning several times. This may go on for several weeks. However, it’s much more common for the rash to move from the cheeks to the child’s body and limbs, and then to clear up completely within a few days.
Although the rash can look quite dramatic at first, the illness itself is usually quite mild. Some children may not even feel ill, while others may have such mild symptoms that the illness may pass unnoticed. This is despite being infected with parvovirus B19, the virus that causes this illness.
Most children will have a mild headache, a sore throat, a runny nose and a mild fever (38 degrees Celsius) that lasts up to 10 days before the rash appears. Occasionally, mild pain, stiffness and even swelling may develop in one or more of the joints for a few days. This is much more common in adults than in children.
In children, fifth disease often occurs as outbreaks at school. The peak times of year for infection to occur is during the winter and spring months.
Fifth disease is typically a mild disease that resolves by itself, leaving no permanent damage. In older children and adults, the disease can cause joint swelling and pain that can last weeks to months. Very rarely, it lasts for a few years.
In children with certain types of hereditary anaemia, such a sickle cell disease and thalassaemia, the disease may be more serious. Fifth disease is also more serious in children and adults who have poor immunity due to illnesses such as cancer, leukaemia or HIV.
What causes fifth disease?
Fifth disease is caused by a virus known as human parvovirus B19 (human PV-B19).
This virus was the first known human virus in the family of viruses known as Parvoviridae. The name is derived from the Latin word “parvum”, which means “small”. This is because the virus is indeed one of the smallest of the DNA viruses.
The parvovirus B19 virus most commonly infects children, but may infect adults, too.
It’s interesting to note that the virus is resistant to most disinfectants.
Risk factors for fifth disease
Children between the ages of 5 and 15 are at greatest risk for fifth disease. If an adult hasn’t been exposed to the virus during childhood, they can also be infected.
School-going children are most at risk of being infected with the parvovirus B19, especially during the winter and spring months of the year.
Adults with poor immunity are most at risk of becoming infected with the parvovirus B19. Examples of illnesses that can affect the immune system in adults include leukaemia, cancer and HIV/AIDS.
Once normal, healthy children have had fifth disease, they develop a lifelong immunity to this illness and cannot get it again.
Course and prognosis of fifth disease
Children and adults who are infected with parvovirus B19 will usually develop symptoms of fifth disease within 4 to 21 days after exposure to the virus (that is, if they haven’t been infected before).
Fifth disease is usually a mild, self-limiting disease, with an excellent outcome and lifelong immunity against reinfection. About 20% of children who become infected with this virus don’t experience any of the typical symptoms (e.g. fever, headache and/or a runny nose).
Of great importance is that there’s a risk of serious complications when a pregnant women becomes infected with the virus. This is also true for people who have compromised immune systems (for example, as a result of HIV/AIDS or cancer) and those with certain hereditary blood disorders (e.g. thalassaemia or sickle cell anaemia).
How is fifth disease diagnosed?
The diagnosis of fifth disease is purely clinical, based largely on the doctor’s examination and the history given by the child, parent or affected adult.
The disease is generally easy to identify by the “slapped cheek” rash that appears on the face and the typical pinkish, lacy rash that appears on the body, arms and legs soon after.
Other illnesses such as scarlet fever, rubella and rheumatic conditions may occasionally mimic the symptoms of fifth disease at first. The symptoms and the rash may be remarkably similar in the early stages of the illness.
Blood tests for antibody levels are sometimes needed, especially if the usual symptoms such as fever, headache and a sore throat are present but the typical rash isn’t. Blood tests are also done if the person’s symptoms are more severe than usual.
Blood tests for parvovirus B19 antibody levels are essential in pregnant women who develop symptoms of fifth disease.
What is the treatment of fifth disease?
Fifth disease is caused by a virus, so it cannot be treated with antibiotics (antibiotics kill bacteria, not viruses).
The symptoms of fifth disease are usually mild and even symptomatic treatment is seldom needed. Children with this illness do, however, need to rest. Once the fever and cold-like symptoms have gone, no further treatment is usually required.
If your child’s rash is itchy, you can ask your doctor if treatment is required for this. The doctor may recommend paracetamol for treatment of fever or any joint pain that may be present. Joint pain is far more common in adults, and treatment for this pain is usually required.
Remember not to give aspirin to your child, as this medication has been linked to a serious illness in children known as Reye syndrome.
In women who are infected during pregnancy, careful follow-up of the unborn child is necessary.
When to call a doctor
Call your doctor if your child develops a rash on their face, especially if the rash is widespread and occurs all over the body. It’s essential to see your doctor if the rash is accompanied by other symptoms (especially joint pain).
Pregnant woman who develop the typical rash of fifth disease, or who have been exposed to someone with fifth disease or an unusual rash, must see their doctor.
Can fifth disease be prevented?
There is no vaccination available to prevent your child from getting fifth disease.
A particular problem in preventing the spread of the disease is that infected people are no longer contagious once the typical rash appears. The rash may take as long as 21 days to appear after the initial infection with parvovirus B19. During this time, the person is contagious.
Washing your hands well and often is always recommended. This remains the most important way of preventing the spread of fifth disease and many other infections.
Reviewed by paediatrician Prof Eugene Weinberg. MBChB; FCP (SA); PAED (SA). March 2018.