A: Roseola is a highly contagious viral infection that's most common in children 6 months to 2 years. It usually starts with a high fever (103 to 105 degrees F.), which can last from three to five days.
You should call your doctor anytime your baby has a fever over 103 F. (for babies under 3 months, call for any fever over 100.4 F.). He'll likely recommend that you try to break the sky-high temperature with acetaminophen. At this point there's no way for sure to know it's roseola; your doctor will only be able to tell for certain after the fever breaks, when a pink, spotty rash will appear, starting on your baby's back, belly, and chest, then spreading outward to the neck, face, arms, and legs.
There's nothing you can do to treat roseola (antibiotics won't help because it's caused by a virus, not bacteria), but it's important to make sure your child gets plenty of fluids to prevent dehydration. Although the rash often looks severe, it's not itchy and your child will actually start feeling better once the spots show up, since the fever will have broken by then.
Since it can sometimes take a week or more after a child's been infected with the virus that causes roseola for the fever to appear, it's easily spread. However, once the rash shows up, your child is no longer contagious.
Copyright 2009 Meredith Corporation.