Roseola infantum, also known as baby measles, is caused by human herpesvirus infection, characterized by acute fever accompanied by a rash. Generally, there is no obvious trigger, and it begins with a sudden high fever, where the temperature can reach up to 39°C or even higher than 40°C. The high fever usually lasts for 3-5 days, during which some may experience fever-induced convulsions. Once the fever subsides, the rash begins to appear. Generally, the rash lasts for 1-2 days. After the rash subsides, and in the absence of complications, the condition resolves.