Health officials expect to see more cases . Swine flu cases may have disappeared , but the 2009 flu virus will probably return . Public health officials to watch Southern California to see what 2009 H1N1 does . Scientists are working on a vaccine against 2009 H1N1 ; wo n't be ready for six months . 2009 H1N1 lacks a gene that is present in very virulent flu viruses , like 1918 strain .
Swine flu cases may have disappeared , but the 2009 flu virus will probably return . Public health officials to watch Southern California to see what 2009 H1N1 does . Scientists are working on a vaccine against 2009 H1N1 ; wo n't be ready for six months . 2009 H1N1 lacks a gene that is present in very virulent flu viruses , like 1918 strain .