Which of the following is a link in the chain of infection?

• A. Pathogen
• B. Recovery
• C. Immunity
• D. Diet

Answer: (A)

The chain of infection consists of steps that must all be present for disease to spread. The essential first link is the pathogen, the microorganism that causes the illness. It’s the agent that can invade a person and be transmitted to another. Recovery represents what happens after infection and is not a step that connects one host to another, so it isn’t a link in the chain. Immunity is the host’s defense that can prevent infection or lessen its impact, reducing susceptibility, but it doesn’t function as the transmission link itself. Diet affects overall health and immune function but isn’t a direct part of the transmission chain. So the organism causing the disease—the pathogen—is the correct link in the chain.