Chapter 15: Infection and Human Immunodeficiency Virus Infection
An infection is an invasion of the body by a pathogen (any microorganism that causes disease)
and the resulting signs and symptoms that develop in response to the invasion.
The most common causes of infection are bacteria, viruses, fungi, and protozoa.
An emerging infection is an infectious disease whose incidence has increased in the past 20
years or threatens to increase in the immediate future.
Emerging infectious diseases can originate from unknown sources, contact with animals,
changes in known diseases, or biologic warfare.
Resistance occurs when pathologic organisms change in ways that decrease the ability of a drug
(or a family of drugs) to treat disease.
Methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE),
and penicillin-resistant Streptococcus pneumoniae are three of the most troublesome antibiotic-
resistant bacteria currently causing problems in North America.
Nosocomial infections are infections that are acquired as a result of exposure to a
microorganism in a hospital setting and typically occur within 72 hours of hospitalization.
For older adult patients, the rate of nosocomial infection is two to three times higher than for
HUMAN IMMUNODEFICIENCY VIRUS INFECTION
The human immunodeficiency virus (HIV) is a ribonucleic acid (RNA) virus, which means it
replicates going from RNA to deoxyribonucleic acid (DNA).
HIV can only be transmitted under specific conditions that allow contact with infected body
fluids, including blood, semen, vaginal secretions, and breast milk. Sexual contact with an HIV-infected partner is the most common mode of transmission.
Immune dysfunction in HIV disease is caused predominantly by damage to and destruction of
CD4 T cells (also known as T helper cells or CD4 T lymphocytes).
The major concern related to immune suppression is the deve