Final answer:
A systemic infection occurs when an infection spreads throughout the body. The main causative organisms can include bacteria like Haemophilus influenzae and Streptococcus pneumoniae, and viruses like varicella-zoster virus and HIV.
Step-by-step explanation:
A systemic infection occurs when an infection spreads throughout the body.
The main causative organisms of systemic infections can vary depending on the specific infection, but some common examples include bacteria like Haemophilus influenzae and Streptococcus pneumoniae, and viruses like varicella-zoster virus and HIV.
These organisms can enter the body through various portals of entry, such as mucous membranes or wounds, and can colonize the circulatory system, leading to serious and potentially fatal infections.