Chapter Eleven:
Preventing Infectious Diseases
© 2013 McGraw-Hill Higher Education. All rights reserved.
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
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– Example: HIV/AIDS
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Pathogens
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Viruses
Prions
Bacteria
Fungi
Protozoa
Rickettsia
Parasitic worms
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Chain of Infection
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Chain of Infection
Agent: Causal pathogen
 Reservoir: Pathogen’s environment
 Portal of exit
 Mode of transmission

– Direct
– Indirect
Port of entry
 New host
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Stages of Infection
Incubation stage
 Prodromal stage
 Clinical stage
 Decline stage
 Recovery stage
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Body Defenses
Mechanical
 Cellular-chemical (“immune system”)
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Divisions of the Immune System
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Cell-mediated immunity
– T cell-mediated
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Humoral immunity
– B cell-mediated
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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
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Immune Response
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Immunizations

Vaccinations should be given against the following
infectious conditions:
Diphtheria
Whooping cough
Hepatitis B
Hepatitis A
Haemophilus influenza
type B
Tetanus
Rubella (German measles)
Measles (red measles)
Polio
Mumps
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Chicken pox
Meningococcus
Pneumococcal infection
Childhood diarrhea
Immunizations Recommended for
Adults
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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
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The Common Cold
(Acute Rhinitis)
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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
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Influenza
Acute viral infection
 More serious than common cold
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– Especially dangerous for young children,
pregnant women, older people
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Annual vaccination

Risk of spread of highly virulent Avian
and H1N1 influenza
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Tuberculosis
Bacterial infection of the lungs
 Symptoms
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– Chronic coughing
– Weight loss
Spread through coughing
 Requires long-term treatment with
antibiotics
 Antibiotic-resistant strains are a concern
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Pneumonia
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Infectious respiratory conditions
– May be bacterial, viral, fungal, rickettsial,
mycoplasmal, or parasitic
– Bacterial is most common, especially
among people with other illnesses
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Vaccination for pneumococcal
pneumonia for children and older adults
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Other Infectious Diseases

Mononucleosis (“mono”)
– Viral infection characterized by weakness, fatigue,
swollen glands, sore throat, and low-grade fever
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Chronic fatigue syndrome
– Characterized by severe exhaustion, fatigue,
aches, and depression
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Bacterial meningitis
– Infection of the thin membranous coverings of the
brain
– Higher risk among college students living in
residence halls
– Immunization available
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Other Infectious Diseases
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Lyme disease
– Bacterial infection transmitted by deer
ticks
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Hantavirus pulmonary syndrome
– Extreme pulmonary distress
– Transmitted from deer mice to humans
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West Nile virus
– Transmitted by mosquitoes
– Flulike symptoms; may involve
encephalitis
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Tampon-related toxic shock
syndrome
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Viral Hepatitis
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Inflammation of the liver
Symptoms
– Fever, nausea, abdominal pain, jaundice
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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)
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Vaccination available for types A and B
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HIV/AIDS
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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)
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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
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– HIV concentration is higher in semen
compared with vaginal secretions
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Diagnosis of HIV Infection
Enzyme linked immunosorbent assay
(ELISA)
 Western BLOT test
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The Course of HIV Infection
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Newly infected may experience flu-like
symptoms within 1 or 2 months of exposure
– Symptoms disappear quickly
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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
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Immune system worsens
– Level of CD4 helper T cells
– Opportunistic infections
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Treatment of HIV Infection
No cure at this time
 HAART (highly active antiretroviral
therapy) can significantly reduce viral
load
 Antiviral drugs
 Drug resistance
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HIV/AIDS on the World Stage
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Prevention of HIV Infection
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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
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Number of Lifetime Sexual Partners
among Adults (Age 20-59)
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Sexually Transmitted Diseases
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HIV/AIDS
Chlamydia
Human
papillomavirus
Gonorrhea
Herpes simplex
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Syphilis
 Pubic lice
 Vaginal infections
 Cystitis and
urethritis
Prevalent STDs
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Chlamydia
– Bacterium Chlamydia trachomatis
– Urethritis
– Left untreated, can cause pelvic
inflammatory disease and infertility in
women
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Human papillomavirus (HPV)
– Often asymptomatic
– Can cause genital warts, cervical cancer
– Vaccine; not curable
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Prevalent STDs
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Gonorrhea
– Bacterium N. gonorrhoea
– Symptoms: painful urination, discharge
– Treated with antibiotics; some strains are drugresistant
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Herpes simplex
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HSV 1 (oral) and HSV II (genital)
Painful blisterlike sores
Pattern of recurrences
Persistent; treated with antiviral drugs
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Prevalent STDs
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Syphilis
– 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
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Pubic lice (“crabs”)
– Cause intense itching
– Treated with prescription and OTC drugs
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Prevalent STDs
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Bed Bugs
– Biologically related to pubic lice
– Commonly found in the folds of bedding, under the edges
of carpets, on draperies, in coat closets, and in clothing
seams.
– Recently became more prevalent because EPA removed
the chemical propoxur from the list of approved indoor
pesticides.
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Prevalent STDs
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Vaginal infections
– Yeast infection (Candida albicans)
– Bacterial vaginosis (BV)
– Protozoa Trichomonas vaginalis
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Cystitis (infection of bladder)
 Urethritis (infection of urethra)
– Caused by various pathogens
– Treated with antibiotics
© 2013 McGraw-Hill Higher Education. All rights reserved.
Chapter Eleven:
Preventing Infectious Diseases
© 2013 McGraw-Hill Higher Education. All rights reserved.