The fifth disease, more properly called infectious erythema, is part of the group of exanthematous diseases proper to childhood, although it can theoretically arise at any age.
It typically affects children from 3-5 years, between the end of winter and the beginning of spring, with epidemic trend at intervals of 4-7 years.
As well as measles, chickenpox, rubella and roseola infantum (sixth disease) is a viral infection.
Causes
The infectious agent responsible is Parvovirus B19, first identified in 1974.
This virus affects only humans and in the body specifically targets bone marrow cells that give rise to red blood cells.
The most common clinical manifestations of the disease, however, are not due to the direct action of the virus, but to the response of the immune system to the infection, with the formation of immune complexes that are deposited in the tissues, especially at the level of the skin and joints.
Symptoms
The appearance of a localized erythema in the cheeks is the typical sign of the disease, possibly followed by a similar rash in the legs and arms.
The exanthema has a characteristic reticulated or “lace” appearance, a symmetrical distribution to both the cheeks and limbs and is generally not itchy.
An inflammation of the peripheral joints (hands, wrists, ankles, knees) can appear early or in conjunction with the exanthema or even later, with greater frequency in adults (in which skin manifestations may also be missing) or in adolescents and much more rarely in children.
The full-blown phase of the disease is often preceded by flu-like symptoms, generally so non-specific and mild that they arouse little attention.
Course
The disease has a possibly prolonged incubation period, from 4 to 20 days, during which the viruses multiply, enter the circulation and are eliminated in large quantities through the respiratory tract incorporated in aerosolized droplets.
The period of contagiousness lasts about a week and coincides with the phase of prodromal symptoms, while the appearance of skin and articular manifestations is practically over and the immune response is already underway.
Exanthemas usually disappear within 1-2 weeks, but can flare up in alternating phases in case of physical or emotional stress or exposure to the sun or contact with hot water.
Joint and muscle pain, when present, usually regress in 2-4 weeks and only in rare cases, and more often in adults, they last for long periods.
Under normal conditions, however, the symptoms resolve spontaneously without requiring any specific treatment.
The stages of the disease are summarized in the following table:
Stage of the disease | Duration |
---|---|
Incubation | 4-20 days |
Contagiousness | About 7 days (coinciding with the phase of prodromal symptoms) |
Duration exanthema | 7-14 days |
Duration of joint pain | 2-4 weeks |
Complications
While in healthy subjects infectious erythema is a completely benign disease, in subjects at risk it can have serious complications.
In patients with blood diseases or immunodepression (haemoglobinopathies, leukaemias, HIV infection) the temporary stop in red blood cell production caused by Parvovirus B19 may result in severe anaemia.
In pregnant women who have not had previous contact with the virus, and are therefore not already immunized, the infection can cause fetal distress and possibly (1-10% of cases) termination of pregnancy.
Prevention
The prevention of contagion is difficult to implement because the spread of viruses occurs at a stage of the infection in which the symptomatology that makes it recognizable is still absent.
Instead, the course of the disease requires careful surveillance in those at risk of developing complications.
Joycelyn Elders is the author and creator of EmpowerEssence, a health and wellness blog. Elders is a respected public health advocate and pediatrician dedicated to promoting general health and well-being.
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