If you're pregnant and already have a little one at home, your practitioner has likely talked to you about precautions to take to avoid exposure to common childhood infections. Fifth disease is one of those common contagious illnesses your child could potentially pass on to you.

While the virus can cause complications during pregnancy, the vast majority of pregnant women who contract it have mild symptoms and deliver healthy babies.

What is fifth disease?

Fifth disease (also known as parvovirus infection or erythema infectiosum) is a very contagious viral illness that's common in kids and is characterized by a "slapped cheek" rash.[1] Fifth disease got its name because it used to be listed as a cause of childhood rash among several rash-causing diseases that are (mostly) rarer today, like measles and rubella.

What causes fifth disease?

Fifth disease is caused by the parvovirus B19 (which, by the way, is not the same virus as parvovirus in dogs and cats). It's spread through saliva or nasal secretions, often via coughs or sneezes, but also simply from close contact with a sick person. 

The virus also spreads through blood, which means it can pass from a mom to baby during pregnancy, although it rarely causes complications. And once you recover, you usually develop immunity that prevents you from getting sick with fifth disease in the future. 

What are the signs of fifth disease?

Many people don't experience any symptoms of fifth disease. Those who do may or may not realize they're sick with the virus, since symptoms are usually mild. 

Fifth disease sometimes begins like a cold; this is the period when you're most contagious. Signs usually show up about four to 14 days after you're exposed to the virus and may include:[2] 

  • Low-grade fever
  • Runny nose 
  • Headache
  • Fatigue 
  • Sore throat
  • Muscle soreness

Fifth disease symptoms in kids

In children, the telltale sign of fifth disease is a bright-red rash on the cheeks that sometimes shows up six to 11 days after other symptoms. (They can look like they've been slapped.) Once your little one gets the rash, he's usually no longer contagious.

A few days later, some kids get a slightly raised rash that starts on the chest and back and spreads to the butt, arms and legs. It can feel itchy, especially on the soles of the feet, and often has a lace-like pattern as it fades. It goes away in seven to 10 days, although the rash may come and go for weeks, tending to crop up when a child is hot from taking a bath or running around outside.

Fifth disease symptoms in adults

Adults with fifth disease are much less likely to get a rash but usually suffer from joint pain or swelling (or both) in the hands, wrists and knees. These symptoms usually resolve in one to three weeks, but they can last several months, though they rarely cause long-term problems.

It is important for patients to know that the virus is most contagious early on, seven to 10 days prior to a rash developing (if it does develop). That's why it's a good idea to reach out to your doctor right away if you think you may have been exposed to the virus.

How common is fifth disease?

Fifth disease is one of the most common childhood diseases. About half of all adults (including pregnant women) are already immune to fifth disease because they got sick with the virus in the past. It can affect people at any age, but is most common in children ages 5 to 15, with outbreaks usually occurring in the late winter and early spring. 

Who is most at risk for fifth disease?

Anyone who isn't immune to the parvovirus B19 from a previous fifth disease infection can catch it, although it causes mild (if any) symptoms in most adults and kids.

The virus can, however, cause complications for people who have anemia or weakened immune systems (from HIV or cancer, or example) as well as unborn babies whose moms contract the virus during pregnancy.

How can I prevent fifth disease during pregnancy?

To reduce the risk of infection, practice good hygiene, especially when you're around small children:

  • Wash your hands for 20 seconds with soap and water often throughout the day and especially after diaper changes and nose-blowings
  • Don't share utensils or cups, especially with young kids
  • Avoid close contact with sick people
  • Don't touch your eyes, nose or mouth with your hands

What should you do if you contract fifth disease during pregnancy?

If you think you might have been exposed to fifth disease during pregnancy, call your practitioner right away. A blood test can show if you're possibly immune to the virus from a previous infection or if you've been recently infected.

The good news is babies are very rarely affected when a mom contracts the virus that causes fifth disease during pregnancy. About half of adults are already immune to the virus, and most people who do get sick during pregnancy have mild symptoms.

In less than 5 percent of women who get sick with fifth disease during pregnancy, the virus can disrupt their baby's ability to produce red blood cells.[3] This may lead to a form of serious anemia that can result in miscarriage or stillbirth. The risks to babies are greater if they're infected during the first half of pregnancy.

If you do get sick with fifth disease during pregnancy, there is no antiviral medication to treat parvovirus B19. Fifth disease doesn't require treatment unless you have risk factors like a weakened immune system or serious complications. Your practitioner will monitor your baby for complications with extra prenatal visits, ultrasounds and blood work.