Exhaustion
You may feel sudden or excessive fatigue which can be a sign that you could be coming down with flu. But, you should know how to discern between general tiredness and excessive exhaustion. Symptoms typically start 1 to 4 days after exposure to the virus and last for around 5 to 7 days, and in some cases much longer. Flu-related fatigue can last for up to 3 weeks, or even longer with.
