A susceptible host is characterized by which of the following?

A susceptible host is characterized by a lack of immunity or physical resistance. This means that the individual does not have adequate defenses to protect against infections or diseases. Susceptible hosts are often unable to mount an effective immune response to pathogens, making them more vulnerable to infections.

This vulnerability can arise from various factors, such as age, underlying health conditions, certain medications that suppress the immune system, or previous illnesses that have weakened their ability to fight off new infections. Recognizing susceptible hosts is crucial in infection control practices, as measures must be taken to protect these individuals from potential infectious agents.

In contrast, the other choices describe traits that do not define a susceptible host. For example, a double immune response implies a strong and capable immune system, which is the opposite of being susceptible. Complete resistance to diseases suggests an immunity level that does not exist in susceptible hosts. Lastly, a sterile environment can help reduce the risk of infection but does not characterize the innate qualities of a susceptible host.