In case of pestilence or epidemic disease, or of danger from anticipated or impending pestilence or epidemic disease, or in case the sanitary condition of any of the said cities should be of such a character as to warrant it, it shall be the duty of the said department of public safety and bureau of health to take such measures, and to do and order and cause to be done, such acts for the preservation of the public health (though not herein or elsewhere authorized) as they may in good faith believe and declare the public safety and health demand.