Sudden diarrhea and watery diarrhea are caused by rotavirus infection, dysentery bacillus infection, abdominal cold, unclean diet, etc. First of all, rotavirus is contagious, once contact with patients suffering from this disease, it will induce the onset of the disease, the attack of the disease is mainly manifested by severe diarrhea, many patients will have watery diarrhea symptoms, and in serious cases, there will be mucus-purulent blood stool. Secondly, dysentery bacillus is a bacterium that is also contagious. Once infected with dysentery bacillus, it will lead to nausea, vomiting, abdominal pain, diarrhea and other symptoms, and the stool that comes out is mainly watery stool. Then some people do not pay attention to keep the abdomen warm at night, resulting in a cold abdomen, and the blood circulation of the intestinal wall is affected when the abdomen is cold. The blood circulation of the intestinal wall will be affected when the abdomen is cold. There will even be ischemia and hypoxia, which will lead to disorders in the absorption function of the intestinal wall, not only will there be symptoms such as abdominal distension and abdominal pain, but some people will also have diarrhea and watery diarrhea. Finally, if you consume unclean or spoiled food, the harmful bacteria in the food will enter the digestive system and cause aggression to the digestive system, and the symptoms of diarrhea and diarrhea will also occur.