According to the Centers for Disease Control and Prevention (CDC), 45 millions American are infected with herpes 1. In up to 80 percent of people, an outbreak is preceded by flu-like symptoms. Flu-like symptoms that herald the onset of a herpes outbreak include fever, headache, muscle pain and malaise.

Fever

Fever is often a presenting symptoms of herpes and may last for two to seven days, according to Dr. Lawrence Corey in "Harrison's Principles of Internal Medicine." This fever is characteristically mild and may not be a “fever” at all–just an elevation over a person’s baseline temperature or a subjective feeling of feverishness. Fever is usually most severe during the initial episode and becomes milder with each recurrence. Fever over 101.3 degrees Fahrenheit during a recurrent episode may signal infection with something other than herpes.

Headache and Muscle Pain

Headache and muscle pain during outbreaks are reported by 80 percent of people, according to a 2005 article in the medical journal American Family Physician 3. These symptoms are more persistent than fever, usually lasting from three to 14 days. Like fever, they become less severe with each recurrence, although they ultimately plateau. In some patients, headache and muscle pain are accompanied by swollen lymph nodes in the groin and the neck.

Malaise

Malaise is single word summary for what people commonly refer to as "feeling sick." Symptoms of malaise may include feelings of lethargy, fatigue, irritability, lack of appetite and non-specific pain. Malaise, according to the CDC, usually precedes the appearance of skin lesions and may persist for the duration of the outbreak.