Final answer:
A systemic infection occurs when the pathogen is spread throughout the body. This differs from local infections that stay confined to one area. Primary infections can sometimes lead to secondary systemic infections when the immune system is compromised.
Step-by-step explanation:
An infection that has spread throughout the body, rather than remaining in one specific area or organ, is called a systemic infection. This type of infection can be contrasted with local or focal infections, which are confined to a small area or a specific site of the body. Systemic infections may result from pathogens entering the bloodstream, causing widespread distribution throughout various organs and tissues. An example of a systemic infection is when the varicella-zoster virus causes chickenpox; it enters through the respiratory system and then causes widespread skin lesions. In some cases, a primary infection can weaken a patient's immune system and make them more susceptible to secondary systemic infections.
A communicable disease is an infectious disease that can be spread from person to person, either directly or indirectly. Communicable diseases can sometimes be contagious, meaning they can be easily transmitted from one individual to another, such as in the case of measles or the flu. However, not all communicable diseases are as contagious as others, as the ease of transmission can vary based upon the pathogen involved.