This viral illness occurs most often in spring, and our practice has been seeing a lot of it.
What is this thing?
Fortunately for most people, it is nothing to worry about. I know the word “disease” makes anything sound awful, but this one merely allows for a history lesson. Several viral and bacterial infections with characteristic rashes used to be numbered. Measles was First, scarlet fever was Second, etc. The only one we still use in practice is Fifth.
Fifth Disease is also known as erythema infectiousum (though this sounds more like a Harry Potter diagnosis), and is caused by a virus called Parvovirus B19. Parvovirus B19 is transmitted by respiratory droplets and causes illness in 3 phases.
- The first phase occurs about a week after exposure and is often mild. It can include mild fever, runny nose, and not feeling well, but for most people is not particularly notable. Some people will have no symptoms at all during this time, though it is the time when you are contagious.
- The next is characterized by rash. This starts as redness on the cheeks, referred to as a “slapped cheek” appearance and is often confused with sunburn. 1-4 days later, redness spreads to the upper arms and legs and becomes lacy in appearance. This fades over the next 1-2 weeks. This rash is sometimes mildly itchy, but not particularly bothersome. Only about 10% of children, and about 60% of adults will have some joint swelling or pain during this phase.
- The last phase involves intermittent reappearance of the rash, typically when hot, exposed to sunlight, or engaging in physical activity.
Like most viral illnesses, this one just takes time and the good work of the body’s immune system to resolve. Once the rash appears and the diagnosis is made, people are no longer contagious and can continue with regular activities.
There are a few groups of people that can have more trouble with Parvovirus B19 because it affects the body’s ability to make red blood cells. We do not worry about this in healthy people as it is brief and resolves quickly. For people with pre-existing anemia or disorders of red blood cell production (like sickle cell anemia), this can cause much bigger problems. Pregnant women who contract Parvovirus B19 for the first time early in their pregnancy can sometimes have problems with their fetuses, but this complication is rare.
So, when do you need to head in to see your doctor?
Clearly if you are concerned that you have Fifth Disease and have an underlying blood disorder, you should be seen by a health care provider. For those who are generally healthy, the primary reason to be seen is to confirm the diagnosis if you are unsure of what is going on. If you know you or your child has had exposure and has the classic rash, it is okay to care for symptoms at home and call or come in if questions arise.