A large number of Britt Elementary School students are still home sick nearly a week after a mysterious illnesses spread throughout the school. Last week, more than 100 out of 600 students were sick, now, officials say 40 of those students remain sick and out of school. Nine more checked out after arriving to school, but of those, only one of those students showed symptoms of the illness. Gwinnett County school officials said they are working with the health department to stop the spread of the highly contagious mystery illness. Since last week, so many students have been sick at the school with diarrhea, vomiting and other symptoms, that the entire building had to be cleaned. Many students who were not infected wore masks to ward off the possible virus. As long as students remain sick, officials said they will continue taking every step to stop it from spreading. "Last night, we brought in cleaners or custodial workers from around the school district, and we cleaned the entire school from top to bottom to make sure we got rid of any germs and that type of thing," said Bernard Watson of the Gwinnett County Schools. "We also cleaned our buses as well." The Gwinnett County Health Department says samples were collected from infected students and sent to labs to determine exactly what the illness was, but they said they will not know the outcome until later in the month. They say the best advice at this point, is to keep your child at home if they are sick, and to remind children how to wash their hands properly.