Cough - As a general rule, if a child has an occasional cough but his energy is up, he's probably not still sick -- tickles and hacks can linger long after a cold has run its course. Dry coughs from allergies and asthma are also not contagious. But if a child has a persistent cough and is acting tired or irritable, he is more likely to be coming down with something. Cough accompanied by a fever should be considered contagious. A barking cough may be croup or whooping cough, while a loud, loose cough from the chest may indicate bronchitis or pneumonia, all of which may be contagious and should be checked out by a doctor.
Fever - A child is sickest the day before a fever begins and for the first three days she is unwell (if it lasts that long). Once a child is under 101°F for 24 hours (without medication), she is much less contagious.
Flu - A child is most contagious the day before she comes down with the flu, and she remains contagious until she is under 101°F for 24 hours (without medication). The fever can last from three to seven days.
Runny Nose - A runny nose is indicative of a cold, which is most contagious for the first three days. Clear, green, yellow, and even rust-colored boogers are all created equal, and while thick, green ones can mean the cold is settling in, they are no more indicative of contagiousness than the clear kind. If the nose is still running after seven to ten days, it can be a sign of a sinus infection, which needs treatment but is not contagious.
Sore Throat - A sore throat with other symptoms, especially fever, is possibly strep or something else contagious, so consult your doctor.
Stomach Bug - Kids are most contagious the day before they begin to vomit or develop diarrhea (which is probably why the darn bugs spread at lightning speed) and remain contagious for the first three days (again, if it lasts) or until they have not vomited or had diarrhea for 24 hours.
