Chapter Eleven: Preventing Infectious Diseases Image source: The McGraw-Hill Companies, Inc./Jill Braaten

Infectious Disease Transmission Pathogen: A disease-causing agent Epidemic: A highly significant increase in the number of cases of an infectious illness existing in a given time period in a given geographical area Pandemic: An epidemic that has crossed national boundaries, thus achieving regional or international status Example: HIV/AIDS

Pathogens Viruses Prions Bacteria Fungi Protozoa Rickettsia Parasitic worms

Chain of Infection Figure 11.1 The Chain of Infection

Chain of Infection Agent: Causal pathogen Reservoir: Pathogen’s environment Portal of exit Mode of transmission Direct Indirect Port of entry New host

Stages of Infection Incubation stage Prodromal stage Clinical stage Decline stage Recovery stage

Body Defenses Mechanical Cellular-chemical (“immune system”) Figure 11.2; The Body’s Defense Systems

Divisions of the Immune System Cell-mediated immunity T cell-mediated Humoral immunity B cell-mediated Acquired immunity Naturally acquired immunity (NAI) Response to naturally occurring pathogen Artificially acquired immunity (AAI) Response to immunization Passively acquired immunity (PAI) From extrinsic antibodies

Immune Response Figure 11-3 The Immune Response

Immunizations Vaccinations should be given against the following infectious conditions: Chicken pox Meningococcus Pneumococcal infection Childhood diarrhea Diphtheria Whooping cough Hepatitis B Hepatitis A Haemophilus influenza type B Tetanus Rubella (German measles) Measles (red measles) Polio Mumps

Immunizations Recommended for Adults Figure 11-4 Immunizations Recommended for Adults

Nosocomial Infections Infections spread in conjunction with the delivery of health care services Between 32,000-100,000 deaths/year are attributed to these infections

The Common Cold (Acute Rhinitis) Acute upper-respiratory-tract infection Caused by different viruses Common symptoms; usually last several days Treatments manage symptoms but do not cure the infection More severe symptoms may indicate flu, pneumonia, or another infection Prevention: Handwashing

Influenza Acute viral infection More serious than common cold Especially dangerous for young children, pregnant women, older people Annual vaccination Risk of spread of highly virulent Avian and H1N1 influenza

Tuberculosis Bacterial infection of the lungs Symptoms Chronic coughing Weight loss Spread through coughing Requires long-term treatment with antibiotics Antibiotic-resistant strains are a concern

Pneumonia Infectious respiratory conditions May be bacterial, viral, fungal, rickettsial, mycoplasmal, or parasitic Bacterial is most common, especially among people with other illnesses Vaccination for pneumococcal pneumonia for children and older adults

Other Infectious Diseases Mononucleosis (“mono”) Viral infection characterized by weakness, fatigue, swollen glands, sore throat, and low-grade fever Chronic fatigue syndrome Characterized by severe exhaustion, fatigue, aches, and depression Bacterial meningitis Infection of the thin membranous coverings of the brain Higher risk among college students living in residence halls Immunization available

Other Infectious Diseases Lyme disease Bacterial infection transmitted by deer ticks Hantavirus pulmonary syndrome Extreme pulmonary distress Transmitted from deer mice to humans West Nile virus Transmitted by mosquitoes Flulike symptoms; may involve encephalitis Tampon-related toxic shock syndrome Image source: Centers for Disease Control and Prevention

Viral Hepatitis Inflammation of the liver Symptoms Types: Fever, nausea, abdominal pain, jaundice Types: Type A – associated with fecal contamination of food due to poor food handling Type B – sexual contact, IV drug use, tattooing, piercing Type C – similar to type B Type D – difficult to treat; found in type B sufferers; contact with bodily fluids Type E – water contamination (rare) Vaccination available for types A and B Image source: The McGraw-Hill Companies, Inc./Christopher Kerrigan, photographer

HIV/AIDS Human immunodeficiency virus (HIV) Acquired immunodeficiency syndrome (AIDS) HIV attacks the helper T cells of the immune system Spread Direct contact involving the exchange of body fluids (blood, semen, vaginal secretions) Sharing of hypodermic needles Infected blood products Perinatal transmission (mother to fetus or newborn)

HIV/AIDS HIV cannot be transmitted by sweat, saliva, or tears, even though trace amounts of HIV are observed Women are at higher risk than men of contracting HIV from an infected partner HIV concentration is higher in semen compared with vaginal secretions

Diagnosis of HIV Infection Enzyme linked immunosorbent assay (ELISA) Western BLOT test

The Course of HIV Infection Newly infected may experience flu-like symptoms within 1 or 2 months of exposure Symptoms disappear quickly Immune system is unable to clear HIV from the body Asymptomatic stage Could last for months to over 12 years Length depends on overall health, age, gender, strain of infection Immune system worsens Level of CD4 helper T cells Opportunistic infections

Treatment of HIV Infection No cure at this time HAART (highly active antiretroviral therapy) can significantly reduce viral load Antiviral drugs Drug resistance Image source: The McGraw-Hill Companies, Inc./Christopher Kerrigan, photographer

Prevention of HIV Infection Learn the sexual history and HIV status of your partner Limit the number of sexual partners Use condoms correctly and consistently Avoid contact with body fluids Curtail the use of drugs Never share hypodermic needles Refrain from sex with known injectable drug users and other high-risk partners Get regular tests for STDs Do not engage in unprotected anal intercourse

Number of Lifetime Sexual Partners among Adults (Age 20-59) Figure 11-5 Number of Lifetime Sexual Partners among Adults Age 20-59

Sexually Transmitted Diseases HIV/AIDS Chlamydia Human papillomavirus Gonorrhea Herpes simplex Syphilis Pubic lice Vaginal infections Cystitis and urethritis

Prevalent STDs Chlamydia Human papillomavirus (HPV) Bacterium Chlamydia trachomatis Urethritis Left untreated, can cause pelvic inflammatory disease and infertility in women Human papillomavirus (HPV) Often asymptomatic Can cause genital warts, cervical cancer Vaccine; not curable

Prevalent STDs Gonorrhea Herpes simplex Bacterium N. gonorrhoea Symptoms: painful urination, discharge Treated with antibiotics; some strains are drug-resistant Herpes simplex HSV 1 (oral) and HSV II (genital) Painful blisterlike sores Pattern of recurrences Persistent; treated with antiviral drugs

Prevalent STDs Syphilis Pubic lice (“crabs”) Bacterium Treponema pallidum Three stages: Primary stage: Painless sore called a chancre Secondary stage: General symptoms of illness Latent stage: May recur many years after initial contact; profound damage to many body systems Left untreated, can cause death Pubic lice (“crabs”) Cause intense itching Treated with prescription and OTC drugs

Prevalent STDs Vaginal infections Cystitis (infection of bladder) Yeast infection (Candida albicans) Bacterial vaginosis (BV) Protozoa Trichomonas vaginalis Cystitis (infection of bladder) Urethritis (infection of urethra) Caused by various pathogens Treated with antibiotics

Chapter Eleven: Preventing Infectious Diseases