It won't be long before we'll be through flu season and will start seeing cases of Fifth Disease. The person or persons responsible for naming this illness didn't have much imagination. Rubella, measles, scarlet fever and roseola were already taken. Since it was the fifth illness described that also caused a skin rash or "exanthem," that's where it got its name. It's also known as "erythema infectiosum."

Fifth Disease cases usually start to show up in late winter and have a second peak in the spring. It's usually seen in kids between five and 15 years of age. The rash is usually of great concern to parents and schools, but by the time it appears, the person is no longer contagious. The time from infection to rash is about two to three weeks.

The cause of the illness, parvovirus type B19, was discovered in 1983. This is not the same virus that causes severe problems in dogs and cats. About 40 to 60 percent of adults test positive for having had the disease at some point in their lifetimes.

The virus is spread via the respiratory route, in a similar fashion to the common cold. An infected family member usually spreads it to about one third of their family. The rate of spread in classrooms is anywhere from 10 to 60 percent. People who have had a prior infection are immune.

The initial illness sometimes resembles a common cold with mild fever, headache and runny nose. Many children have no symptoms until they develop a rash. The rash usually appears in three stages, but they are not always distinguishable. The first stage is a very characteristic flushing of the cheeks, often described as a "slapped cheek" appearance. The rash then spreads rapidly to the trunk, upper arms and legs. It then becomes less prominent and takes on a lacy appearance. It does not involve the palms or soles.

The rash usually goes away over one to three weeks and may come and go. It can be worsened with exposure to sunlight, heat, stress and exercise. Children, as well as adults, can get fairly severe joint pain that commonly lasts two to four weeks, but sometimes for months. Joint pain is more common in women and is more severe in adults.

There are people that need to be concerned about exposure to the virus. Patients with suppressed immune systems from chemotherapy or other illnesses such as HIV can have prolonged problems, especially anemia. People that have diseases involving the breakdown of red blood cells (sickle cell, thalassemia, etc.) are also more prone to develop severe anemia.

The virus can cross the placenta from mother to baby. It can cause severe anemia in about 5 percent of pregnancies. This, in turn, can lead to heart failure and loss of the baby. It is therefore recommended that pregnant women, especially in their second trimester, be careful around children when there is an outbreak of Fifth Disease in the community.

There is no antiviral treatment for Fifth Disease like there is for influenza. Severely ill patients are occasionally given IV immune globulin that contains antibodies to try and slow the infection. The vast majority of those infected with parvovirus B19 have mild illness and make full recoveries.