gastroenteritis

What i mean is when there is a sudden outbreak, where does it start from, what is the source of it, and how does it start???

both of my daughters have this and they also have alot of coughing, is this normal?

Hi, my son's gf hardly seems to eat much of meals! she is NOT underweight though. she said she can fancy something but when she goes to eat it she can only manage some of it as she will start to feel sick. she says this happened after having Gastroenteritis.