USA HISTORY

Detailed explanation-1: -Smallpox is contagious, but it’s spread less easily than illnesses like influenza or measles.

Detailed explanation-2: -The pathogens that can be easily disseminated or transmitted from person to person are the riskiest for clinicians (Ebola virus, Marburg virus, Lassa virus, Crimean-Congo hemorrhagic fever virus, Variola major, SARS virus and Yersinia pestis).

Detailed explanation-3: -Measles is one of the most contagious diseases Measles is so contagious that if one person has it, up to 90% of the people close to that person who are not immune will also become infected. Infected people can spread measles to others from four days before through four days after the rash appears.

Detailed explanation-4: -Smallpox and measles are two of the most contagious infectious diseases and have had a profound effect on human history. They were present in ancient times, but few clinical descriptions of these two major infectious disease entities exist in early medical writings [1].