Chapter 11 Reducing the Risk for Infectious Disease J. Don Chaney, Ph.D. Texas A&M University

Reducing the Risk for Infectious Disease Infectious disease: communicable or contagious disease; caused by pathogens, such as bacteria or viruses, that spread from someone who is infected to someone who is not yet infected. Chain of Infection: a metaphor for infectious disease transmission in which each link in the chain represents a single factor necessary for disease to spread.

Table 11.1 Reducing the Risk for Infectious Disease Table

Table 11.1 Reducing the Risk for Infectious Disease (cont'd.)

Reducing the Risk for Infectious Disease Chain of Infection Causative agent: a microorganism that causes disease. Pathogen: a microorganism, such as a bacterium, that causes disease. Reservoir of the pathogen: place (either a human or an animal) where a pathogen resides. Portal of exit: the means by which the pathogen moves out of the source into a new host.

How Diseases Are Spread Chain of Infection, cont’d. There are five means of transmission: air, direct contact, contaminated food or water, vectors, pathogens exiting body. Vectors: insects or animals that carry disease. Means of entry into the host Host susceptibility Eradication

How Diseases Are Spread Causes of Infection Bacteria: single-celled, plant-like microbes that act to produce symptoms of infection. Toxins: poisonous substances produced by a microorganism. Viruses: chains of nucleic acid surrounded by a protein coat that invades cells and uses the cells’ reproductive capabilities.

How Diseases Are Spread Causes of Infection Viruses: the most primitive form of life and can reproduce on their own. Secondary infection: an infection that occurs in conjunction with, or as a result of, another infection but arises from a different pathogen. Interferon: a chemical substance produced by the white blood cells that “interferes” with growth of a virus and also inhibits the virus’ ability to infect cells; also made synthetically. Protozoa: single-celled parasites that produce toxins and release enzymes that interrupt the body’s ability to function normally.

How Diseases Are Spread Causes of Infection cont’d. Parasitic worms Fungi Allergen Rickettsia Prions

How Diseases Are Spread How Infections Get Into Your Body Through the air Through physical contact Contaminated food and water Vectors Already in the body

How Diseases Are Spread Why Doesn’t Everyone Get Sick? Virulence: the strength of pathogens present during disease transmission. Dosage: amount of pathogens present during transmission. Resistance: the capacity of the immune system to fight the invasion of an organism.

How Diseases Are Spread Nonspecific Defense Mechanisms The body’s various barriers to all disease; as opposed to those defense mechanisms intended to prevent one particular disease. Mucous membranes: the moist, protective lining that covers some of the openings to the body and the air passages. Phagocytes: white blood cells that attack and consume foreign cells. Inflammation: the body’s response to injury; it fights infection and promotes healing.

How Diseases Are Spread Specific Lines of Defense Active immunity: the body’s development of its own resistance to disease. Passive immunity: resistance to disease initially from an external source. Antibodies are specific proteins that are produced principally in the blood in response to foreign substances in the body. Antigens: foreign substances in the body that cause the production of antibodies. Herd immunity: the vaccination of a large proportion of a population against a particular disease.

Stages of Infectious Disease Incubation Prodromal stage Acute stage Convalescence Recovery

Table 11.2 Common Infectious Diseases

Table 11.2 Common Infectious Diseases (cont'd.)

Common Infectious Diseases Common Cold Influenza Influenza is a severe viral infection involving the respiratory tract. Pneumonia Bacterial Pneumonia Mycoplasmas Fungal Pneumonia

Common Infectious Diseases Tuberculosis Mononucleosis Chronic Fatigue Syndrome Meningitis Urinary Tract Infection (URIs)

Common Infectious Diseases Childhood Diseases Mumps Rubella (German Measles) Measles MMR vaccine

Sexually Transmitted Infections Prevention and Treatment In almost all cases, only sexually active people are exposed to STIs. An individual must have sex with a person who is infected. The risk for being exposed to an STI decreases when prophylactics are used.

How Do You Know If You Have an STI? Unusual discharge from the vagina or penis Burning pain, stinging, or irritation when passing urine A sore, blister, ulcer, warts, or break in skin, or rash in the genital area A low abdominal pain or pain during intercourse

How Do You Know If You Have an STI? Safer Sex A pattern of responsible sexual behavior characterized by reduced risk for disease A willingness to prepare ahead for sex A commitment to using condoms Truly understanding that if you are sexually active you can get STIs

Table 11.3 Common Sexually Transmitted Infections

Table 11.3 Common Sexually Transmitted Infections (cont'd.)

Common Sexually Transmitted Infections Viral Infections Hepatitis: an inflammation of the liver, usually caused by a virus. Hepatitis A: transmitted by human wastes and contaminated food and water. Hepatitis B: transmitted by blood and sexual contact. Hepatitis C is a type of hepatitis that resembles other forms of hepatitis but cannot be classified as either.

Common Sexually Transmitted Infections Viral Infections cont’d. Acquired Immune Deficiency Syndrome (AIDS) is a combination of symptoms caused by the human immunodeficiency virus (HIV). Helper T-Cells: white blood cells that are needed by the body’s immune system to fight a variety of disease-causing organisms. Opportunistic diseases: diseases common to individuals infected with HIV that under normal conditions would be defeated by the body’s immune system. Kaposi’s Sarcoma: a rare, deadly cancer characterized by reddish-purple blotches on the skin.

Common Sexually Transmitted Infections Viral Infections cont’d. Human Papilloma Virus (HPV): the agent responsible for STI characterized by warts, usually on the genitalia; also called genital warts. Herpes Simplex Type 2: a virus usually transmitted by sexual contact and causing open sores on the genitals. Meningitis: an inflammation of the membranes surrounding the spinal cord and brain. Systemic Infection: an infection affecting the body as a whole.

Common Sexually Transmitted Infections Bacterial Infections Chlamydia: causes serious, painful infections of the urinary tract in men and infection of the reproductive organs in women. Pelvic Inflammatory Disease (PID): an infection usually involving the uterus, fallopian tubes, and/or ovaries; half the cases are caused by chlamydia. Gonorrhea: a widespread infection; symptoms include a burning sensation during urination. Syphilis Primary syphilis Secondary syphilis Late syphilis

Common Sexually Transmitted Infections Other STIs Vaginitis Yeast Infection Protozoal Vaginitis Trichomoniasis

Common Sexually Transmitted Infections Emerging Diseases West Nile Virus: causes death by encephalitis, an inflammation of the brain. Cutaneous anthrax Inhalation anthrax Gastrointestinal anthrax

Protection Through Prevention Reducing Your Risk for an Infectious Disease Maintain overall good health. Practice basic hygiene. Keep your vaccinations up-to-date. Treat all minor infections seriously. Support your local public health authority.