Fifth disease, also known as erythema infectiosum, is a viral illness caused by human parvovirus B19. The term “fifth disease” refers to the fifth of the 6 rash-associated diseases of childhood.
Parvovirus B19 commonly causes a “slapped-cheek” rash on the face and, less commonly, fever, headaches, sore throat and joint pain. In adults, it may cause arthralgias (painful joints) in addition to the characteristic skin rash. These symptoms are more common in adult women than in men. They usually last for 2-4 weeks but may persist for months.
In some cases fifth disease can cause anemia. In healthy individuals, this anemia is mild and only lasts a short period of time. However, in individuals with weakened immune systems such as AIDS patients, transplant recipients or cancer patients, this anemia can be severe and last long after the infection has subsided. Symptoms of anemia include fatigue, lack of colour and shortness of breath. Some individuals with sickle cell anemia or iron deficiency may develop a potentially life threatening disorder called transient aplastic crisis, where the body is unable to form new red blood cells.
In very rare cases, fifth disease may cause swelling of different areas of the body including the brain (encephalitis), the sheath around the brain and spinal chord (meningitis) and the lungs (pneumonitis). The virus can also cause worsening symptoms in individuals who suffer from the autoimmune disease, systemic lupus erythematosus.
Many people with fifth disease show no symptoms at all. Therefore, the only way to definitively diagnose it is to have a test. Approximately 50-60% of adults have had the disease and are immune. However, those who are not immune may be at risk from picking up this infection, particularly healthcare providers, childcare providers and teachers.
Fifth disease is transmitted primarily by respiratory secretions (saliva, mucous etc.) but can also be spread by contact with infected blood. The incubation period (the time between the initial infection and the onset of symptoms) is usually between 4 and 21 days. Individuals with fifth disease are most infectious before the onset of symptoms. Typically, school children, day-care workers, teachers and mothers are most likely to be exposed to the virus. When symptoms are evident, there is little risk of transmission; therefore, infected individuals need not be isolated.
The New England Journal of Medicine
In a recent New England Journal of Medicine paper (N. Engl. J. Med. 350;6) entitled “Mechanisms of Disease: Parvovirus B19”, Parvovirus B19 is dicussed in detail.The authors cover Parvovirus B19-associated diseases, pathophysiology, clinical diagnosis and treatment and prevention. This paper is directed at physicians and healthcare providers.