There is an observed rise in cases of acute gastroenteritis and post-infectious irritable bowel syndrome (PI-IBS) during the peak flood period. One major reason is poor sanitation, water and hygiene practice by flood victims during the flood because of poor access to clean water. The mechanism how poor hygiene causes non-specific abdominal complaints is unknown. The investigators speculated that small intestinal overgrowth (SIBO) is the fundamental basis for the increase in reported cases of acute gastroenteritis and abdominal complaints among flood victims. The investigators further speculated that administration of antibiotics or probiotics could reduce the abdominal symptoms after three months.