Origin, symptoms and treatments: the fifth disease explained

This contagious infection, often asymptomatic, primarily affects children aged 4 to 10 years. In adults, it can prove dangerous for pregnant women, immunocompromised persons or those with certain forms of anaemia. MonacoSanté keeps you informed.

Incubation, contagiousness and immunity

Erythema infectiosum, parvovirus B19, slapped cheek disease: three names for the same eruptive childhood pathology, more commonly known as the fifth disease. This designation is explained by its place in the list of infections most frequently causing skin rash in children, after measles, scarlet fever, rubella and scalded skin syndrome, whilst roseola occupies the sixth position. "Parvovirus B19 is the cause of this infection, which manifests as a skin rash, particularly on the cheeks. However, it can also go completely unnoticed. Its incubation period lasts 4 to 21 days, which gives it a high degree of contagiousness because the patient transmits the infection even before the disease manifests itself", explainsDr Barbara Macchi Lam, general practitioner in Monaco. The patient also remains contagious during the first phase of the fifth disease, during which only appear. However, they are no longer contagious once the rash develops. This condition is transmitted by respiratory droplets suspended in the air (coughing, sneezing, spitting), but also through contact with contaminated objects or the hands of an infected person. "In very young children, it can be transmitted by the exchange of dummies", the doctor points out. 

Infections in spring and autumn

According to data from French Public Health, cases multiplied in France between 2023 and 2024. A trend that aligns with the observations of Dr Macchi Lam, established in the Principality for three years, who has treated many infected patients during this same period. The disease primarily affects children aged 4 to 10 years but also unimmunised adults. "Infections occur mainly during the inter-seasons, in spring and autumn. The good news is that once contracted, the disease confers lasting immunity", the doctor explains. It is estimated that approximately 50% of young adults have already been infected, sometimes without knowing it, as infection does not always result in symptoms. "In some patients, the manifestations result in redness on the cheeks, fever and skin rashes on the arms, legs and trunk". In approximately 15% of cases, these patches cause itching. "On the hands and feet, small red spots that do not disappear under pressure, called purpura, may also appear joint pains in the hands, wrists and knees can also be felt", the healthcare professional continues. A disease sometimes unknown to the general public, easily confused with the effects of the first rays of sunshine. "A mother came for a consultation for her young child, thinking he had simply got sunburn. But it was indeed the virus that was responsible". In the vast majority of cases, the fifth disease remains mild in children. "If they are in good health, it is supposed to go away as it came". 

When to Consult?

"When dealing with any childhood pathology, the doctor looks at their general clinical condition. Even with fever and red cheeks, if they have a normal attitude, we are not concerned. On the other hand, if they are very tired and pale, this becomes worrying", considers Dr Macchi Lam. In a healthy child, this viral infection generally does not require specific treatment. "We may give paracetamol to relieve the fever. For the spots, no cream, as the redness disappears on its own". A diagnosis can, however, be confirmed by a blood test: "We look for the presence of immunoglobulins specific to parvovirus B19 type IgM or IgG to determine whether it is a recent or past infection". Consultation becomes mandatory, however, in the event of appearance of purpura, a "worrying warning sign" not to be overlooked, in both children and adults. "In this case, we ensure there are no signs of meningitis, a serious disease which can cause purpura, and we carry out a blood test to check that the platelet count is not too low". Another reason for emergency consultation: intense pallor, rapid breathing, extreme fatigue, or fainting. All symptoms that could suggest sudden anaemia. 

Adult profiles requiring enhanced vigilance

Finally, if you are pregnant, have symptoms of infection and feel that your baby's movements are decreasing, you must see a specialist very quickly. Dr Macchi Lam alerts to the profiles of adults most at risk immunocompromised persons, those with red blood cell disorders and pregnant women. "The latter is particularly exposed. Because being pregnant does mean having a slight immunosuppression", she explains, highlighting the risk of mother-to-child transmission. Indeed, an infection during pregnancy, especially before 20 weeks, can lead to serious complications for the foetus, such as severe anaemias or generalised oedema. To prevent these situations, she recommends early screening via a blood test looking for parvovirus IgG, in order to know whether the patient is immunised. Immunocompromised persons, for their part, are exposed to an increased risk of anaemia, as are individuals already suffering from red blood cell pathologies, such as rare diseases like sickle cell disease or thalassaemia, the virus attacking these cells directly. If these forms generally remain transitory, the doctor insists on the need to identify these at-risk profiles and avoid any exposure, even if treatments can be considered in certain cases.

Limiting spread and protecting at-risk persons

In the face of the fifth disease, vigilance and communication are essential. "If you have a diagnosis and you have seen people at risk, you must warn them", she emphasises, particularly in the event of contact with a pregnant woman, so that she can quickly consult a specialist. At home and in communal settings, simple measures can limit transmission: wearing a mask in the presence of vulnerable persons, regular airing of rooms and strict hygiene. Often mild, the fifth disease remains an infection to be monitored, particularly in certain vulnerable populations. Better understanding its symptoms, its modes of transmission and the at-risk profiles allows us to adopt the right reflexes at the right time.