Cysts can arise through a variety of processes in the body, including.  1 wear and tear or simple obstructions to the flow of fluid, 2  infections, 3  tumors, 4  chronic inflammatory conditions, 5  genetic (inherited) conditions,  defects in developing organs in the embryo.
1 Acute * sinusitis often develops after a person has had a cold, with symptoms lasting less than 3 weeks. 2  Chronic * sinusitis can last 3 to 8 weeks or longer; it often occurs in people who have allergies or asthma. 3  Recurrent sinusitis consists of several acute episodes of sinusitis in 1 year.
You can be contagious from a few days up to two weeks or more, depending on which virus is causing your stomach flu (gastroenteritis).A number of viruses can cause gastroenteritis, including noroviruses and rotaviruses.The contagious period â the time during which a sick person can give the illness to others â is slightly different for each virus. 1  Norovirus.2  With norovirus â the most common cause of viral gastroenteritis in adults and children â you're contagious from the moment you begin to feel ill. number of viruses can cause gastroenteritis, including noroviruses and rotaviruses. The contagious period â the time during which a sick person can give the illness to others â is slightly different for each virus.