The autonomic nervous system (ANS) regulates the functions of our internal organs (the viscera) such as the heart, stomach and intestines.
The flu is contagious a day before and five days to a week after its onset. Young children, people over 65, those with compromised immune systems, and people with a terminal illness are at risk of death from the flu.
The typical flu incubation period is between 24 hours and four days, with the average being two days. This means that if you are exposed to the influenza virus and become infected, you will start to experience flu symptoms anywhere between 24 hours and four days after the exposure. Another factor that contributes to how the flu spreads is when exactly you may be contagious.