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Infectious Disease
Major Pathogens
Pathogen: Organisms that causes disease
Types of pathogens include:
Viruses, Bacteria, Fungi, Protozoan, Parasitic worms, Prions
Chain of Infection
•Pathogen – An organism the causes diseases (These include bacteria, viruses, fungi, protozoa, parasitic worms, &
prions).
•Reservoir –the natural environment of the pathogen: a person, an animal, or an environmental component like soil or
water. If a person is the reservoir, they may or may not appear to be ill or have symptoms, but still be able to pass on
(transmit) the pathogen.
•Portal of exit – where the pathogen leaves the reservoir: saliva, mucous membranes, blood, feces, & nose or throat
discharges.
•Means of transmission – Transmission can occur directly or indirectly
Transmission Routes
•Direct transmission--the pathogen is passed from one person to another without an intermediate component. Direct
contact usually requires a close proximity, but it doesn’t have to be direct physical contact, can be inhaled, sexual
contact, blood to blood.
•Indirect transmission occurs when the pathogen is passed to the new host using an intermediate component
•Vector is an insect, rodent, or other organism (ticks, mosquitoes, other animals) that carries and transmits a pathogen
from one host to another.
•Fomite- inanimate object that transfers a pathogen: soil, food, or water, & by eating utensils, doorknobs, & tissues
Portal of Entry
To infect a new host, the pathogen has to have a way to get in.
1. Penetration of the skin or direct contact
2. Inhalation through the mouth or nose
3. Ingestion of contaminated food or water
•Localized infection-only in the surrounding tissues
•Systemic infection- spread infection throughout the body
Breaking the Chain
Interfering with any of the steps of the chain of infection: public health measures (sanitation/regulations) & personal
actions (washing hands/healthy lifestyles/safe sex)
Inflammatory Response
•When the body has been infected, one of the responses is the Inflammatory Response
•Special cells release histamine which causes heat, swelling, and redness of that area
•White blood cells attack the invader, attempting to destroy them
How Does A Person Achieve Immunity?
•After an infection, lymphocytes created during the amplification phase of the immune response serve as memory T
and B (antibodies) cells
•They continue to circulate in the blood and lymphatic system for years or even longer
•If the same antigen enters the body, the T and B recognize this and destroy it
•The ability to have lymphocytes remember previous infections is known as acquired immunity
5 Stages of an Infection
–Incubation stage: bacteria or virus multiply, usually without symptoms
–Prodromal stage: Initial symptoms, host doesn’t feel ill, highly contagious
–Clinical stage: height of the disease, person is usually at home or hospital, less likely to transmit
–Decline stage: decrease severity of symptoms, relapse may occur
–Recovery stage: person may feel well, may still be infectious
Treating Bacterial Infections and Viruses
•Antibiotics kill bacterial infections
•Vaccines can limit your exposure to viruses, but no true cure for viruses.
Immunizations
•Vaccinations are when the immune system is given an antigen which is not considered dangerous
•The body produces antibodies, which prevent serious infection against that particular disease
•Vaccines are made by either weakened pathogens or killed pathogens, which still illicit the production of antibodies
(active immunity), or antibodies can be injected (passive immunity) to create temporary immunity
Allergies: The Body’s Defense Gone Haywire
•50 million Americans are affected by allergies
•This is a result from a hypersensitive and overactive immune system
•The immune system mounts an attack on a harmless substance
•The results create the unpleasant and potentially serious symptoms of an allergy
•Allergens: Pollen, Animal dander, Dust mites and cockroaches, Medication, Types of metals, Mold and mildew,
Foods, Insect stings, Plants, Substances found in cosmetic products
The Allergic Response
•Most allergic reactions are due to the production of immunoglobulin E (IgE)
•Mast cells release large amounts of histamines and other compounds into the surrounding tissue
•Histamine has many effects, such as congestion, redness, swelling, etc. but the most serious kind of allergic reaction is
anaphylaxis
Bacterial Infections
•Meningitis
•Tuberculosis- kills over 3 million people a year- it’s back!
•Pneumonia
•Strep Throat and other streptococcal infections
•Urinary Tract Infections
•E Coli- undercooked beef, sanitation
•Lyme disease and other Tickborne infections
•Tetanus
Viral Infections
•HIV
•Common Cold
•Influenza
•Hanta Virus- contact with rodents, mouse droppings, flu-like symptoms leading to respiratory distress
•Chicken Pox, Cold sores, and herpes virus infections
•Ebola- mainly found in African nations, massive internal bleeding, bleeding from the skin, injections sites- BAD
NEWS!
•Viral Hepatitis- Hep C
Fungal Infections
•A fungus is a primitive plant
•50 of thousands of fungi cause disease among humans
•Candida albicans is a common fungus found naturally in the vagina of most women, which causes infections (yeast
infections)
•Other common forms are athlete’s foot, jock itch, and ringworm
•Fungal infections can be deadly in people with impaired immune systems
Parasitic Worms
•Considered the largest organism that can enter the body to cause infection
•Worms, including the tapeworm and hookworm, can grow to a length of many feet, especially in the intestinal tract
•Worm infections can originate from contaminated food or drink
Emerging Infectious Diseases
•Selected Infections of Concern: SARS, E. coli , Hantavirus, Monkey Pox, Ebola, Avian flu
•Emerging Infectious Diseases: infectious diseases globally are a major killer: new diseases, resurgence of TB &
cholera & spread such as Ebola or West Nile virus.
Public Health Concerns
•Drug Resistance: Antibiotic resistance bacteria, over application of antibiotics
•Poverty: lack access to drugs, overcrowding, migration spread of disease
•The breakdown of public health measures—related to poverty and funding, laziness
•Environmental changes: change in land use and rainfall brings vectors & contact with new diseases
•Travel & Commerce—5 million travelers cross national borders each year-spreading disease
•Mass food production and Distribution—food travels long distance and mass production runs risk of mass distribution
of disease
•Human Behaviors--injection drug use, sexual behavior, daycare use
Incidence vs. Prevalence
•Incidence: number of new cases of a disease within a specified period of time, usually 1 year
•Prevalence: overall occurrence: the total number of cases of a disease
•Incurable diseases look at prevalence, short term diseases look at incidence
•Be sure when comparing statistics you know which one was used.
HIV Infection
•It is estimated that more than 60 million people have been infected with HIV
•By 2004, it is estimated that 1 million Americans are living with HIV
•HIV infection continues to spread, even though death rates have declined among Americans, however, a cure has not
been discovered
•Locally, HIV is on the rise again- Why?
What is HIV?
•Cause – HIV, virus that attacks the CD4 T cells of the immune system
•What is AIDS?
•A-Acquired: because it is not inherited
•I-Immuno: because it affects the immune system
•D-deficiency: because the body lacks immunity
•S-syndrome: because the symptoms occur as a group
HIV Transmission
–Blood products
–Sharing instruments used to inject drugs
–Anal and vaginal intercourse
–Oral sex
–Transmission of HIV during pregnancy and/or birth
–Mother to child through breast milk
Body Fluids that the HIV virus
Can Survive in:
•Blood
•Semen: including pre-cum
•Vaginal Fluids
•Breast Milk
Cannot Survive in:
•Tears
•Sweat
•Urine
•Saliva
HIV Infection
•Following several weeks after becoming infected, about half of those develop flu-like symptoms (Primary Infection
Phase)
•Experts believe that half of all HIV cases are spread during this phase
•The next phase is known as the Chronic Asymptomatic Stage which can last 2-20 years
•During this time, the virus is progressively infecting and destroying cells of the immune system
Symptoms of HIV Infection and AIDS
•Unexplained persistent fatigue
•Fever, chills, night sweats
•Unexplained weight loss
•Swollen lymph nodes
•Pink, red, purple, or brown blotches
•Persistent dry cough
•Persistent, fuzzy, white spots in mouth, tongue, or throat
•Persistent diarrhea
•Memory loss or depression
•Abnormal pap smears
•Persistent vaginal candidiasis
•Abdominal cramping (due to PID)
Populations of Special Concern for HIV Infection
•Although the transmission of HIV occurs through specific individual behaviors, high levels of infection within certain
groups are tied to social, cultural, and economic factors
•Such groups that are affected are: IV drug users, men and women not utilizing condoms when having sex,
homosexual men, men who are having sex with other men but do not consider themselves homosexual, minorities, poor
HIV Diagnosis: Types of tests
ELISA - enzyme-linked immunosorbent assay (Screening)
Western blot—more specific
Rapid HIV test – A drop of blood, results in 20 mins
Notifying current and past partners
Treatment of HIV/AIDS
Anti-HIV medications
AZT (zidovudine)
Reverse transcriptase
Protease
“AIDS cocktail”
Therapies to treat symptoms & infections
Drugs that affect virus in some way
Treatments designed to bolster immune system’s natural responses
How Can You Protect Yourself?
Learn the sexual history and HIV status of your partner
Limit the number of sexual partners
Use lubricated 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
Get regular tests for STD’s
Participate in an HIV Education Program
Sexually Transmitted Infections-Chlamydia
Bacterium – most prevalent in the U.S.
Symptoms in males include: Painful urination, Slight watery discharge, Pain in the testes
Symptoms in women include: Vaginal discharge, Burning urination, Lower abdominal pain
Diagnosis: urine sample, fluid from infected site
Treatment: antibiotics
Transmission: unprotected vaginal & anal sex
Sexually Transmitted Infections
•Gonorrhea- Bacteria – estimated 700,000 new cases in the United States annually-antibiotics
•Pelvic Inflammatory Disease- usually occurs when gonorrhea or chlamydia travels past the cervix- leading cause of
infertility in young women- antibiotics
•HPV (virus) – genital warts which can lead to cervical cancer in women & penile cancer in men- growths that cause
irritation and bleed- no cure.
•Genital Herpes- Caused by HS2 (Herpes Simplex 2 virus) which is sexually transmitted even though the partner may
appear asymptomatic-Herpes lesions may contain and transmit HIV- no cure, antiviral will decrease symptoms
Hepatitis
•Hepatitis A, B, C, D, E: Virus
•Inflammation of the liver
•Symptoms – fever, nausea, abdominal pain, jaundice, dark urine
•Type A – associated with fecal contamination of food due to poor food handling, found in the stool of an infected
person, poor sanitation, contaminated water sources- Vaccination
•Type B – sexual contact, IV drug use, tattooing, piercing, occupational exposure- Vaccination series
•Type C – similar to type B- no vaccination, treatment is interferon and ribaviron- makes you very sick!
•Type D- similar to type B
•Type E- similar to A
What Can You Do?
•Education
•USE PROTECTION WHEN HAVING SEX!
•Get Vaccinated
•Be Alert for possible symptoms
•Get Tested
•Inform your partners
•Get Treatment