Nurses and the control of infectious disease. Understanding epidemiology and disease transmission is vital to nursing care.

Epidemiology examines the distribution and source of a disease in a population. Understanding epidemiology and disease transmission is vital to nursing care. Infectious disease transmission requires three components: an agent (virus, bacterium, parasite or other microbe), a vulnerable host and a conducive environment. Disease spread can occur through direct contact or via indirect methods (airborne droplets, vectors, fomites, water or food). Intervention can occur by attacking the agent (e.g., using microbicides), changing the environment (e.g., providing negative pressure rooms) or strengthening the host (e.g., vaccination). Three epidemiologically relevant microbes are the SARS (severe acute respiratory syndrome)-associated coronavirus, methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile (C. difficile). The first is an emerging pathogen, and the latter two are existing agents that have mutated such that they are resistant to their standard treatments. For SARS, control measures include screening for possible cases and appropriate triage, respiratory and barrier precautions within the healthcare facility, and voluntary isolation in the community for contacts or healthcare workers who exhibit symptoms. Control measures for MRSA include the screening of patient lesions, isolating or cohorting patients who are already infected, covering wounds with impermeable dressings, treating staff and patient carriers with antibiotics, and improved hygiene. Control measures for C. difficile Control measures include paying close attention to the hygiene of the clinical setting, disinfecting using bleach and the isolation of infected patients.