Fifth disease ( erythema infectiosum) is a viral illness caused by human parvovirus B19.It is most often seen in children ages 4 to 14.
There are many kinds of parvoviruses. This one has no connection to the types which infect dogs or cats.
The infection starts with a mild fever, sore throat, headache and cold-like symptoms. A few days later, these symptoms pass and a bright red rash appears on the face. It gives the child a "slapped cheek" appearance. During the next few days the rash spreads to the trunk, arms and legs. By this time, child is usually no longer infectious.
The child is most contagious before the rash appears, during the incubation stage or when mild respiratory symptoms are present. Therefore it is easy to be exposed to the disease without being immediately aware of it.
The virus is spread through secretions from the nose or lungs, or through contact with blood. Good hygiene and washing hands offers the best protection against many infections, including this one.
For most children, the disease is mild and no treatment is necessary. However, there may be cause for concern when a pregnant woman becomes infected. This does not happen often.
About 50% of adults have had the disease and possess antibodies, which will protect both a mother and her unborn child. A blood test can tell if you have antibodies and are therefore immune, or if you have had a recent infection. Because the disease is mild, you may not even remember having had it as a child.
If you are pregnant, and you think you have no immunity, and have been exposed to a family member with fifth disease, you have a 50% chance of being infected. You should inform your obstetrician.
During the first trimester of pregnancy, there is a 20% chance of miscarriage if the baby develops the disease. After 20 weeks, the risk drops to 1%.
If the foetus is infected, it can develop inflammation of the heart (myocarditis), and bone marrow damage. The child could not then produce red blood cells. This can lead to anemia. If heart damage or anemiais severe, hydrops can occur. Hydrops is a condition wherein there is excess fluid in fetal tissues, and it can result in fetal death.
Sometimes, the hydrops disappears and most of these babies are born normal. Rarely, a child who is born unable to make red blood cells will require transfusions.
When a pregnant woman has tested positive for fifth disease, frequent ultrasound tests are recommended to check for hydrops. Successful fetal blood transfusions have been done during the second and third trimesters. During the third trimester, if the baby is showing signs of hydrops, an early delivery may be considered.
The little known name "fifth disease" comes from an early classification of childhood diseases which produce rashes. They are: (1) measles, (2) chicken pox, (3) German measles, (4) roseola and the fifth disease.
Often in normal, healthy children, it is a mild illness and may even pass unnoticed. It is only in the earliest stages of life, when the child is still in its mother's womb that the fifth disease may pose a significant threat. With good prenatal care and the marvels of modern medicine, much can be done to allay the danger of even that.