Highly contagious diseases are caused by various biological agents that pose a risk to individuals and may have a potential for public health impact. They result in high mortality and morbidity rates, might cause public panic and therefore require special measures.
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). Human-to-human transmission has not been confirmed for the other biological agents and therefore they pose a very low risk for healthcare workers.