gastroenteritis contagious period
1 Rotavirus. 2  Symptoms of rotavirus â the leading cause of viral gastroenteritis in infants and young children â usually appear one to three days after exposure. 3  But you're contagious even before you develop symptoms, and up to two weeks after you've recovered.he 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.