Causes of DiseaseCauses of DiseaseChapter 16Section 1

ObjectivesObjectivesIdentify five common types of

pathogenDescribe three ways infectious

disseases are spreadDistinguish between infectious

diseases and communicable diseases

Identify two causes of non-infectious diseases

Key TermsKey TermsPathogenInfectious diseaseInfectionToxinCommunicable diseaseAIDSHIV

Infectious DiseasesInfectious Diseases• Caused by a pathogen• The pathogen invades the body

and begins to reproduce• There are five important

pathogens–Bacteria–Protozoa–Fungi–Worms–Viruses

BacteriaBacteriaSimple single celled organismsThey live everywhere

◦On every surface◦Including the inside and outside of

your bodyThey are microscopic

◦Cannot be seen without “help”Some are harmful, but some are

helpful◦Toxins result from harmful bacteria

ProtozoaProtozoaSingle celled organismsMicroscopic, but larger than

bacteriaFound in most water supplies

◦Not bottled or filtered water◦Most are not dangerous

FungiFungiMolds and mushrooms are the

most common examples of FungiMany are beneficial to humansSome are pathogens

◦Athlete’s Foot◦Ringworm◦Thrush

WormsWormsWorms can enter the body in a

variety of waysThey are usually immature when they

enterThey move to specific tissues or

organs as they maturePathogenic worms

◦From the environment Hookworms from the soil

◦From food Trichina from raw or undercooked meats

VirusesVirusesMuch smaller that most bacteriaA virus is not a cell based

organism◦It is made of a protein coat◦It contains a type of genetic material

They only reproduce inside other cells◦It takes over the cell◦Destroys the cell◦Infects nearby cells

More about Infectious More about Infectious DiseaseDiseaseThe ability of one person or

organism to transfer the infection to another person or organism describes a communicable disease

Some diseases do not transfer well from one individual to another

A highly infectious disease may stay in one kind of organism◦“bird flu” found in poultry◦Not HIV, found in several types of

organism

AIDSAIDSAIDS is a communicable disease

caused by a virusAIDS is caused by HIVIt is possible to test for AIDSThere are treatments, but as yet

no cure for AIDS

See page 522, Table 16.1 to see methods of disease transmission

Non-Infectious DiseasesNon-Infectious DiseasesNOT caused by pathogensNOT communicableThese diseases may be inherited

◦Muscular dystrophy, sickle cell anemia, cancer

These diseases may be caused by the environment or exposure to toxins◦Cancer, heart diseases, arthritis

SummarySummaryInfectious diseases are caused by

pathogens◦Bacteria, protozoa, fungi, worms, and

virusesPathogens invade the body, reproduce,

causing an infectionCommunicable diseases are infectious

diseases that can be spread from person to person

Non-infectious diseases are NOT caused by pathogens, but by genetic factors, the environment, or both

DefinitionsDefinitionsPathogen is a virus or

microorganism that causes disease

Infectious disease is an illness caused by a pathogen

Infection is the invasion and multiplication of pathogens in the body

Toxin is a poisonous substance

DefinitionsDefinitionsCommunicable disease is an

infection that can be spread from person to person

AIDS, (acquired immuno-deficiency syndrome) is a viral disease that destroys the body’s ability to resist other diseases by disrupting the immune system

HIV, human immuno-deficiency virus) is the virus that causes AIDS