Fifth disease

Fifth disease, also known as erythema infectiosum, is a contagious viral infection. It's called fifth disease because it's number five in a group of childhood diseases that cause fever and rash. The condi- tion is most common in children, and more than half of all people have contracted it by adulthood. Outbreaks are most common from late winter through early summer, especially in school and child care settings. Fifth disease is considered a mild condition, but it can cause serious complications if contracted during pregnancy.


Causes/associated factors
Fifth disease is caused by human parvovirus B19. Again, about 50 percent of adults have had a bout with fifth disease and develop immunity to the condition. Anyone who hasn't had the disease is susceptible, however, and most people don't know if they've ever had it.
Parents with young children and those who work in child care or health care settings face an increased risk of exposure to fifth disease. Susceptible people have a 50 percent chance of developing fifth disease if a household member contracts the infection. Outbreaks in school may result in 10 to 60 percent of children becoming infected.


Transmission
The virus can spread through contaminated blood products and respiratory secretions, such as sputum, nasal mucus or saliva. Secretions may spread through direct contact with an infected person, sharing his or her cups or utensils, or breathing in droplets coughed or sneezed into the air. This isn't the same parvovirus that infects animals, so transmission to or from animals isn't possible. People are thought to be most contagious five to 10 days before the rash appears, and most are no longer contagious once the rash appears. The incubation period (the time from exposure until symptoms appear) is about four to 20 days.

Signs/symptoms
Fifth disease is usually mild and may even go unnoticed. About 25 percent of infected adults don't develop symptoms. If symptoms appear, you may first notice a low-grade fever, headache, sore throat, runny nose, muscle or joint pain, abdominal pain, nausea or diarrhea. These initial symptoms, called prodromal symptoms, may be followed by a characteristic rash that typically appears suddenly, making your cheeks bright red. This rash is less common in adults.
Next, a flat or raised red rash may appear on your torso and extremities. Eventually, the rash will fade in the center, creating a lacy appearance. It may seem more pronounced with sunlight exposure, friction, exercise, stress or heat, such as warm bath water.The rash may last weeks or months and may be itchy at times, especially for adults.

Many adults, especially women, develop painful, swollen or stiff joints without a rash. The hands, wrists, ankles and knees are most often affected. After several weeks to months, the symptoms usually disappear completely.

Some adults develop a glove-and-stocking syndrome with an itchy, fine, red rash on the hands and feet. Fever and mouth sores may also appear.


Diagnosis
Your doctor may suspect fifth disease based on your symptoms or your exposure to an infected person. Blood tests for certain antibodies (substances that help neutralize or destroy foreign substances in the blood) can help your doctor determine if you have the infection or are already immune to fifth disease.

Treatment
Acetaminophen, aspirin (except for children age 19 or younger), or ibuprofen can be used to treat the fever and pain associated with fifth disease. Over-the-counter antihistamine tablets or hydrocortisone creams may relieve the itching. Adults may need to restrict their activities due to joint pain and swelling. People with weak immune systems who contract the virus may need therapy with intravenous immune globulin (a protein that can act as an antibody).

Complications
For people who have weak immune systems (such those who have HIV, cancer or organ transplants) or chronic red blood cell disorders (such as sickle cell anemia), fifth disease can lead to severe anemia that requires medical attention, possibly including a blood transfusion.

Pregnancy-specific information
If you've been exposed to fifth disease, contact your doctor. Your blood will be tested for susceptibility. If you contract the infection during pregnancy, it won't necessarily affect the baby. If the baby does become infected with fifth disease, however, it can interfere with the baby's ability to make red blood cells. This can lead to:
severe fetal anemia (a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron)
miscarriage
stillbirth
premature birth
hydrops fetalis (swelling that can cause serious heart problems)
If you've been exposed and the antibody test doesn't show you've been infected, the test will be repeated in three to four weeks. If the second test is negative, your baby isn't at risk for infection. If the test result is positive, your doctor will begin monitoring your baby for infection. Hydrops fetalis and other serious complications can be detected with repeated ultrasounds (using sound waves to create an image of internal body parts). If the baby develops hydrops fetalis, the doctor may recommend an intrauterine blood transfusion. Sometimes, the condition resolves without treatment.

For women who develop fifth disease during the first half of pregnancy, the risk of fetal death from the disease is less than 10 percent. The risk drops even lower during the second half of the pregnancy.


Senior-specific information
Growing older isn't a risk factor for developing fifth disease.

Prevention
There's currently no vaccine to prevent fifth disease. To decrease your risk of infection, wash your hands often, especially after touching tissues used by infected people. Also, don't share eating utensils with anyone who has the infection or has been exposed to the disease. If you're pregnant, minimize contact with anyone who has the infection or has been exposed to the disease.