In July 2004, researchers led by H. Deng of the Harbin Veterinary Research Institute, Harbin, China, and Robert Webster of the St. Jude Children's Research Hospital, Memphis, Tennessee, reported results of experiments in which mice had been exposed to 21 isolates of confirmed H5N1 strains obtained from ducks in China between 1999 and 2002. They found "a clear temporal pattern of progressively increasing pathogenicity."[15] Results reported by Webster in July 2005 reveal further progression toward pathogenicity in mice and longer virus shedding by ducks.