© Jennifer Summer

More than 200 students at an Humble ISD elementary school didn't make it to campus Thursday, after a flu-like illness swept the school on Wednesday.The school - Woodland Hills Elementary - has an enrollment of 581 students.Parents may be keeping their students off the campus as a precaution.The half-empty campus comes after 78 students did not come to class and more were sent home on Wednesday, according to a letter from the school's principal.As of Thursday morning, district officials did not know the cause of the illness. The city of Houston Health Department is investigating its cause, district spokeswoman Robin McAdams said.Students who mention any kind of discomfort will be sent home, even if they don't have a temperature, McAdams added."Right now, if a child complains they're not feeling well, they're going home," McAdams said.The illness did not appear to have spread to other Humble ISD campuses, as of Thursday morning.The campus was sanitized on Wednesday night, and will continue to be sanitized every night until further notice, McAdams said."As a precaution, Humble ISD custodial services are sanitizing the school and will conduct another thorough cleaning tonight," the principal wrote Wednesday.The classrooms, from the desks to the doorknobs, are being scoured by hand every night. Then, special equipment is used to fog the interior of the school and all buses that drop kids off at the campus with antibacterial mist, McAdams said.The Harris County Health Department also asked to speak to a small group of parents as they investigate and determine if additional steps are needed for prevention.The letter asked parents to keep children home if they exhibit symptoms of stomach ache or diarrhea.