If blood tests have been done testing for virus or bacteria and is clear of both. what can be causing my childs fever and coughing?

Tests ????: I know of no tests that exclude the possibility of a virus or bacteria triggering fever in anyone a any time. Several will provide useful information on severity or imply one vs the other but there is no such test.Fever is a non-specific natural body defense that increases metabolism & circulation to fight illness. Coughing is a natural defense that removes debris from deeper in the lung.