Some of the earliest signs of the flu include the sudden onset of excessive fatigue, aches and chills, coughing and chest tightness, soreness in the throat, fever and gastrointestinal problems, such as nausea, stomach pain, vomiting and diarrhea. Some early symptoms require emergency medical attention, according to Healthline. These include chest pain, difficulties breathing, a bluish color on the skin and lips, severe dehydration, dizziness, confusion and a recurring fever.
Of the symptoms listed, fatigue is typically one of the first to manifest, according to Healthline. It tends to be more severe in the case of flu than it is in the case of the common cold virus.