A polio expert with the World Health Organization joins the Minnesota Department of Health as the state's epidemiologist. Dr. Harry Hull will succeed Michael Osterholm, who left the state epidemiologist post last year to start a consulting firm. Before going to the World Health Organization, Dr. Hull was the state epidemiologist for new Mexico. In that position, he says that he spent time dealing with anti-smoking campaigns, immunizations and the state's first cases of AIDS. But he also dealt with a disease that is very rare.