ASCP Phlebotomy Technician Certification Practice Exam 2026 – Comprehensive All-in-One Study Guide for Success!

The factor that best increases a host's susceptibility in the chain of infection is drug use. Individuals who use drugs, particularly those that impair the immune system such as immunosuppressive drugs or illicit substances, can be more vulnerable to infections. This increased susceptibility arises because drug use may compromise the body's natural defenses, making it easier for pathogens to invade and cause disease.

Age, nutrition, and hygiene are all important factors that can influence susceptibility as well, but their impact can vary significantly across different populations or individuals. While poor nutrition can weaken immunity and old age can present its own challenges to the immune system, drug use directly and often dramatically alters immune response and physiological functions, leading to a significant increase in susceptibility to infections.

Thus, focusing on drug use as an influence highlights a critical area for public health interventions aimed at reducing infection risk in vulnerable populations. Understanding these dynamics aids in developing effective prevention strategies in phlebotomy and wider healthcare practices.