Final answer:
A susceptible host is an organism that is invaded and often harmed by a pathogen. Some individuals may be more susceptible to infections due to various factors, such as compromised immune systems or preexisting conditions. Herd immunity is a phenomenon where the presence of immune individuals in a population protects even the susceptible individuals from the spread of a disease.
Step-by-step explanation:
A susceptible host is an organism that is invaded and often harmed by a pathogen. Pathogens, such as bacteria, protists, fungi, and other infectious organisms, can cause diseases in their hosts. Some individuals may be more susceptible to infections due to preexisting conditions, environmental factors, or genetic immune factors.
For example, individuals with compromised immune systems, the very young or the elderly, pregnant women, patients undergoing chemotherapy, and those recovering from surgery are more susceptible to opportunistic infections.
Herd immunity is another concept related to susceptible hosts, where the presence of immune individuals in a population protects even the susceptible individuals from the spread of a disease.