What does the term 'carriers' refer to in the context of infectious diseases?

In the context of infectious diseases, the term 'carriers' specifically refers to individuals who harbor disease-causing microorganisms after recovery from the illness but do not exhibit symptoms themselves. These carriers can still transmit the pathogens to others, playing a crucial role in the spread of infections within a community. For example, someone who has recovered from a disease like typhoid fever can continue to carry the bacteria in their body and potentially infect others, even though they do not display any signs of illness.

The other options do not accurately define carriers in this context. Individuals who show symptoms and require treatment are actively ill and not classified as carriers since they are expressing the disease. Those who eliminate the microorganisms completely after recovery would not be considered carriers either, as they would no longer harbor the pathogens. Similarly, people who are immune to infections have developed a resistance and do not harbor the pathogens, making them distinct from carriers. Therefore, the concept of carriers is vital in understanding how infectious diseases can persist and propagate within populations.