Herpes viruses typically infect the oral or genital mucosa. Most oral herpes virus infections are due to the virus known as HSV-1, while genital herpes virus infections are most often caused by HSV-2. However, both kinds of herpes virus can infect any location in the body. When herpes affects the mouth, it causes the typical "cold sores" or painful blisters that form on the lips, mouth, or gums. Prior to the development of the blisters, there may be an itching, burning, or tingling sensation in the affected area. The virus remains dormant in the nervous system throughout life, and this is the reason that cold sores often recur in the same location. Herpes infection of the genital tract is a sexually transmitted infection. Like in the mouth area, herpes symptoms include a painful, blistering rash around or on the genital or rectal areas. The blisters open and result in painful sores that can take two to four weeks to heal. Recurrent outbreaks are typical, and the time between outbreaks varies among affected people and even within the same individual. Prior to an outbreak, a tingling, burning, or itching sensation may be present on the area of involved skin. With the first outbreak of herpes virus infection, an individual may also experience nonspecific flu-like symptoms like fever, swollen lymph nodes, and muscle aches. It is also possible to have herpes virus infection without having any symptoms, or having symptoms that are so mild that the infection is mistaken for another condition.