Introduction to Infectious Disease

Infectious Disease – Key Terms

• Infectious – can spread • Disease – an abnormal condition affecting the

body of an organism• Pathogens – “germs”; what causes disease

Germ Theory through the AgesGerm Theory – states that diseases are caused by microorganisms

Before

Before Germ Theory…• Theory of “Spontaneous Generation” – diseases were simply an unfortunate

occurrence due to chance & probability

Think about it….

Significant Historical Developments in Infectious Disease & Germ

Theory

Anton van Leeuwenhoek

• First microbiologist; Dutch; 1670s• Used microscopes to observe and identify

microscopic living organisms

Ignaz Semmelweis• Vienna, 1840s

“Childbirth fever”

Louis Pasteur• France, 1859 – Curved Flask Experiment

• Essentially the definitive demonstration negating spontaneous generation

Joseph Lister• Lister, 1860s:

Antiseptics• Washed wounds to

prevent infections during surgery

Taxonomy and Infectious Disease• What types of pathogens cause infectious diseases?• In what taxonomic kingdoms are they classified?

Taxonomy and Infectious Disease

Prokarya

Eukarya

Archaebacteria

Eubacteria

Protista

Fungi

Plantae

Animalia

Autotrophic

Pathogen 1: Bacteria• Living

– Kingdom Eubacteria (although only a small fraction of this kingdom are pathogenic)

• Structure– Prokaryotic cells– Produce toxins that harm host (parasitic)

Exam

ples

Pathogen 2: Viruses• Non-living!!!!

– Infect host and take over cellular metabolism to construct new viruses

• Structure:– DNA or RNA core– Contained in protein

capsid– Protein spikes to

attach to host cells– Some have a

membranous envelope

– Shape can vary but all viruses are typically symmetrical

Examples: HIV, Influenza, Ebola, Chickenpox

Pathogen 3: Fungi• Living – Kingdom Fungi• Structure:– Eukaryotic– Chitin cell wall– Heterotrophic (by absorbing nutrients from host)

• Examples: Ringworm, Yeast Infections, Athlete’s Foot

Pathogen 4: Parasites• Living – Kingdoms Protista & Animalia• Structures:– Protozoans – single celled organisms– Helminthes – worms– Animal structures – mosquitoes, fleas, ticks

• Transmitted through ingestion of eggs & insect bites• Examples: Malaria, Tapeworm, Bubonic Plague

Pathogen 5: Prions• Non-living• Structure– Misfolded proteins

that cause brain and neural damage, eventually fatal

• Examples: Mad Cow Disease, Creutzfeldt-Jakob Disease (CJD)

Classroom Activity: “History-Altering” Infectious Diseases

1. Your group will be assigned 1 infectious disease that altered history.2. Research that disease with your group on www.cdc.gov or other reliable sources about one of the following diseases:

• Smallpox in Native American populations during Age of Exploration/Colonialism • Tuberculosis in Industrial Revolution age (“The Great White Plague”), • Bubonic Plague in Europe (“Black Death”)• Cholera in England (England 1800s), • Yellow fever in the Panama Canal, • Typhus (body lice) during the Thirty Years War• Polio in late 19th-early 20th century; • Biology/plant life extension: potato blight (cause of the Irish potato famine), • 1918 influenza in America (“Great Influenza” “Spanish flu” “Flu of 1918”)• H1N1 Bird flu• Swine flu