Roseolovirus is the name for two different types of herpes viruses -- human herpes viruses 6 and 7. As with other types of herpes, they're transmitted primarily through saliva and other bodily fluids. Although HHV-6 and 7 differ slightly in the way that they replicate in the body, they're very similar genetically.
Most people who are infected with HHV-6 don't have any symptoms. Those who do will experience them before the age of 2, and by this age, almost 100 percent of children in the United States have it [source: HHV-6 Foundation]. It usually presents as roseola, a rash also known as rose fever or baby measles (although there's no relation to measles). Before getting the rash, children often run a high fever and have swollen lymph nodes. The rash consists of flat pinkish red spots that usually start on the trunk and spread to the rest of the body. The high fever can cause seizures in some children with roseola, so it needs to be treated with acetaminophen or ibuprofen. In rare cases, it can cause problems with the nervous system or gastrointestinal tract. Otherwise, the rash and other symptoms usually subside within a few weeks without any lasting problems. Most children who get roseola never have it again.
Adults rarely get HHV-6. When they do, it's usually in the presence of other diseases such as AIDS or cancer, which cause a suppression of the immune system response. In many cases, these adults have already had HHV-6 but their weakened immune systems can't suppress reactivation of the virus. HHV-6 in adults can cause more serious symptoms such as hepatitis and encephalitis. It's also been linked to some types of cancer, including acute lymphoblastic leukemia, multiple myeloma and Hodgkin's disease.
HHV-7 isn't as well understood as HHV6. It's found in most of the population in the United States, but people are usually infected with it as adults rather than as children. It's also believed to cause roseola, but some researchers believe that it's a roseolalike illness called pityriasis rosea rather than roseola. HHV-7 has been linked to hepatitis in adults.
Although AIDS patients are often more susceptible to the severe complications of all types of herpes, the eighth type of herpes is most often directly associated with an AIDS-related disease. Next, let's look at Kaposi's sarcoma.