Hi. Thanks for your query. Noted the history and understood your concerns. If all of your friends including you are suffering from bad tummy cramps, diarrhea and feeling sick at the same work place the obvious causes are as follows: Intestinal infection due to the food source if you all are eating at the mess/canteen or water source as you have mentioned. This can be stomach flu too. This can be diagnosed by the following ways: Get the water sample and food samples checked for contamination by the respective authority. Use only boiled and cooled water. Get the stool and blood samples checked and if the infection or infestation is found you all will be treated accordingly to get the cure. Use water and soap every time anyone visits the bathrooms. Watch for the preventive causes as discussed and everyone will be fine.