When a health officer has reason to believe that a disease that endangers public health exists within the county, the health officer shall: Report immediately to the appropriate county board of health; and With the approval of the board: Investigate the suspected disease; and Act properly to prevent the spread of the disease. Except in Baltimore City, the attending physician of an individual who has the disease may act properly to prevent the spread of the disease and does not need the approval of the county board of health to act. A physician may act under this paragraph only until the health officer completes the investigation under paragraph (1) of this subsection or, if sooner, until the emergency ends. A county board of health shall pay the necessary and legitimate expenses that a health officer incurs under this subsection. When a health officer is notified of an infectious or contagious disease within the county, the health officer: Shall act immediately to prevent the spread of the disease; Within 24 hours after receiving notice of the disease, shall give the Secretary all information obtained on the disease; and Shall cooperate with the Secretary to prevent the spread of the disease. When a health officer knows of any unusual disease or mortality in the county or a contiguous county, the health officer promptly shall give the Secretary notice of the disease or mortality. If a health officer is unsure whether a disease is infectious or contagious, the health officer shall notify the Secretary.