Infectious Diseases

© Lisa Michalek

Pathogens

• Disease causing agents that have the ability to make you sick or even cause death

• They are found in the air and food and on nearly every object or person who you come in contact with

Uncontrollable Risk Factors

• Heredity– Chromosomal traits and family history

• Aging– Vulnerability increases with age

• Environmental Conditions– Unsanitary conditions, drugs, chemicals, and

pollutants

• Organism Resistance– Some pathogens are resistant to our body’s

defenses and/or medical treatments

Controllable Risk Factors

• Stress

• Nutrition

• Physical fitness level

• Sleep

• Drug use

• Hygiene

• High-risk behaviors

Routes of Pathogen Transmission• Direct Contact

– Touching, kissing, sexual relations

• Indirect Contact– Touching an object that an infected person

has had contact with

• Airborne Contact– Breathing in air that carries

a pathogen

• Food-borne infection– Eating something that is

contaminated by microorganisms

Routes of Pathogen Transmission

• Animal-borne pathogens– Animals can spread diseases through bites, feces, or

by carrying infected insects into living areas

• Water-borne diseases– Transmitted from drinking water, from foods washed or

sprayed with contaminated water, or from wading or swimming in contaminated streams, lakes or reservoirs

• Perinatally– Mothers can transmit diseases to an infant in the womb

or as the baby passes through the vagina during birth

Bacteria• Single-celled organisms • There are several thousands of species, but

only about 100 cause diseases in humans• Most of the time it is not the bacteria that is

causing the diseases, but it is the toxins that are produced by the bacteria

• They can be seen under a standard microscope

Bacterial Diseases• Staphylococcal Infections

– These bacteria are normally on our skin at all times and usually do not cause problems

– When a cut or break in the skin occurs, the bacteria may enter and cause an infection

– Acne, boils, styes (eyelid infections), wounds are common staph infections

Bacterial Diseases• Streptococcal

Infections– Causes strep throat

and scarlet fever

• Pneumonia– One form is caused by a

bacterial infection with the following symptoms: chronic cough, chest pain, chills, high fever, fluid accumulation and eventual respiratory failure

Bacterial Diseases• Legionnaire’s Disease

– A water-borne disease with symptoms similar to those of pneumonia

• Tuberculosis (TB)– An airborne disease where

bacteria infiltrate the lungs and cause a chronic inflammatory reaction

– Symptoms include coughing, weight loss, fever and spitting up blood

Viruses• Minute (very tiny) parasitic microbes that live

inside another cell• Over 150 viruses are known to cause diseases

in humans• Viral diseases

are hard to treat because many can withstand heat, chemicals and large doses of radiation with little effect on their structure

Viral Diseases• The Common Cold

– There may be over 200 different viruses responsible

– Carried into the nose and throat most of the time

– Stress, allergies, and menstrual cycles appear to increase susceptibility

Viral Diseases• Influenza (flu)

– Symptoms include aches and pains, nausea, diarrhea, fever, and cold like ailments

– In healthy people, it is usually not serious– However, when

combined with other disorders, among the elderly, those with respiratory or heart disease, children under 5 the flu can be very serious

Viral Diseases• Mononucleosis (mono or the kissing disease)

– Symptoms include sore throat, fever, headache, nausea, chills, weakness or tiredness, lymph nodes may swell, jaundice (yellow skin), spleen enlargement, aching joints, and body rashes may occur

– May be transmitted through body fluids but does not appear to be easily contracted through normal, everyday contact

Viral Diseases

• Hepatitis– Causes inflammation of the liver – Symptoms include fever, headache, nausea,

loss of appetite, skin rashes, pain in the upper right abdomen, dark yellow urine, and jaundice

Viral Diseases– Hepatitis A (HAV)

• Contracted from eating food or drinking water contaminated with human feces

– Hepatitis B (HBV)• Spread through body fluids, usually during unprotected

sex• Can lead to liver disease or liver cancer

– Hepatitis C (HBC)• Some cases can be traced from people who share

needles, blood transfusions or organ transplants• Usually causes chronic infections and if not treated

may cause cirrhosis of the liver, liver cancer, or liver failure

Viral Diseases• Measles

– Symptoms appear about 10 days after exposure and include an itchy rash and a high fever and may lead to other problems such as rheumatic heart disease, kidney damage and neurological disorders

Other Pathogens• Fungi

– Multicellular or unicellular primitive plants that inhabit our environment

– Many are useful providing food such as mushrooms and cheeses

– Some produce infections• Candidiasis (vaginal)• Athlete’s foot• Ringworm• Jock itch

Other Pathogens• Protozoa

– Microscopic, single-celled organisms that can cause disease• Trichomoniasis

– transmitted sexually

• Giardiasis– found in water

• Malaria– Via mosquitoes

Other Pathogens• Parasitic Worms

– Usually associated with eating raw fish– Cooking fish and other foods to high

temperatures will kill the worms and their eggs to prevent infestation

• Pinworms• Tapeworms

The Immune System• Protects the body from potentially harmful

substances• Any substance

that is capable oftriggering an immune responseis an antigen

• When invadedby an antigen, the body forms antibodies to destroy or weaken the antigen

Vaccines• A vaccination consists of an injection of a dead

or weakened form of a disease-causing microorganism.

• This organism can no longer cause the disease, but can still stimulate antibody production by white blood cells.

• This type of immunity lasts a long time.