For the purpose of this article, maximum incubation periods shall be considered to be as follows: Chickenpox, 18 days; measles, 18 days; German measles, 21 days; typhoid and paratyphoid fevers, 28 days; acute poliomyelitis, 14 days; Rocky Mountain spotted fever, 12 days; scarlet fever, seven days; whooping cough, 16 days; diphtheria, seven days; epidemic meningitis, 14 days; mumps, 26 days; smallpox, 21 days. (Ord. 4404)