A literature survey identified 1,407 recognized species of human pathogens, 58% of which are zoonotic. Of these, 177 are classified as emerging or reemerging, with zoonotic pathogens being twice as likely to be in this category as nonzoonotic ones. Emerging and reemerging pathogens are not strongly associated with particular nonhuman hosts but are most likely to have broad host ranges. These pathogens are associated with various drivers, with changes in land use, agriculture, and demographic changes being most commonly cited. Although zoonotic pathogens are the most likely source of emerging and reemerging diseases, only a small minority have caused major epidemics. The study revisited these findings using updated data on pathogen biology and epidemiology. It examined differences between major pathogen groups—viruses, bacteria, fungi, protozoa, and helminths—and their host ranges and emergence factors. Zoonotic pathogens are more likely to be emerging or reemerging, with 73% of emerging or reemerging pathogens being zoonotic. Host range varied across pathogen groups, with ungulates being the most important overall. Emerging and reemerging pathogens showed a trend of increasing fraction with broader host ranges, though this was not significant for protozoa and helminths. Drivers of emergence included changes in land use, agriculture, hospitalization, and international travel. Emerging and reemerging pathogens are not strongly associated with particular host types, but they often have broad host ranges. Most zoonotic pathogens are not highly transmissible between humans, though some can cause major epidemics. The basic reproduction number (R0) determines outbreak size, with pathogens having R0 close to 1 being particularly sensitive to small changes. The study highlights the diversity of emerging and reemerging pathogens, emphasizing the need for broad surveillance and monitoring. Given that three-fourths of these pathogens are zoonotic, surveillance should also include potential animal reservoirs.A literature survey identified 1,407 recognized species of human pathogens, 58% of which are zoonotic. Of these, 177 are classified as emerging or reemerging, with zoonotic pathogens being twice as likely to be in this category as nonzoonotic ones. Emerging and reemerging pathogens are not strongly associated with particular nonhuman hosts but are most likely to have broad host ranges. These pathogens are associated with various drivers, with changes in land use, agriculture, and demographic changes being most commonly cited. Although zoonotic pathogens are the most likely source of emerging and reemerging diseases, only a small minority have caused major epidemics. The study revisited these findings using updated data on pathogen biology and epidemiology. It examined differences between major pathogen groups—viruses, bacteria, fungi, protozoa, and helminths—and their host ranges and emergence factors. Zoonotic pathogens are more likely to be emerging or reemerging, with 73% of emerging or reemerging pathogens being zoonotic. Host range varied across pathogen groups, with ungulates being the most important overall. Emerging and reemerging pathogens showed a trend of increasing fraction with broader host ranges, though this was not significant for protozoa and helminths. Drivers of emergence included changes in land use, agriculture, hospitalization, and international travel. Emerging and reemerging pathogens are not strongly associated with particular host types, but they often have broad host ranges. Most zoonotic pathogens are not highly transmissible between humans, though some can cause major epidemics. The basic reproduction number (R0) determines outbreak size, with pathogens having R0 close to 1 being particularly sensitive to small changes. The study highlights the diversity of emerging and reemerging pathogens, emphasizing the need for broad surveillance and monitoring. Given that three-fourths of these pathogens are zoonotic, surveillance should also include potential animal reservoirs.