What makes us sick?…

…pathogens make us sick  An organism or substance that causes disease  Contains an antigen- substance that triggers an immune response  Examples  Bacteria (streptococcus)  Viruses (influenza)  Fungi (ringworm)  Worms (tapeworm)  Protists (malaria)  Toxins/venoms (exotoxin)

What makes a good pathogen?  Multiplies rapidly  Fools the immune system  Doesn’t kill its host  Survives for a while outside the host

Viruses Discovered in 1898 by Friedrich Loeffler and Paul Frosch (foot in mouth disease) Infectious particle smaller than any bacteria ( nanometers) Depend on host cell to reproduce Not necessarily considered living

Virus structure and mechanism Protein capsule + DNA or RNA (retroviruses have RNA) Infected cell produces viral DNA & protein instead of its own proteins smallpox, cold, chickenpox, influenza, herpes, polio, rabies, Ebola, hanta, Generally can only infect you once

Retrovirus Best example: HIV (human immunodeficiency virus) Contains RNA and reverse transcriptase enzyme Enters cell and reverse transcribes RNA into DNA DNA inserts itself into host cell genome DNA instructs cell to make HIV proteins & RNA Proteins self-assemble and bud out of the cell membrane New virus takes a piece of the membrane with it

Retroviral action

Bacteria Kingdom Monera: prokaryotic cells Kingdom Monera: prokaryotic cells Single-celled organisms found virtually everywhere (500 species in your mouth) Single-celled organisms found virtually everywhere (500 species in your mouth) Different shapes, colors, sizes (20 nm-1 mm), cell wall components, energy, motility Different shapes, colors, sizes (20 nm-1 mm), cell wall components, energy, motility Live freely in and out of host Live freely in and out of host E. coli, streptococcus, staphylococcus, anthrax, plague E. coli, streptococcus, staphylococcus, anthrax, plague

How do we get infected? Modes of transmission: Modes of transmission: Direct contact: with open sores or body fluids (hands, mouth, genitals) Direct contact: with open sores or body fluids (hands, mouth, genitals) Indirect contact: food, water, doorknobs, etc. can be contaminated with a pathogen Indirect contact: food, water, doorknobs, etc. can be contaminated with a pathogen Inhaling airborne pathogens Inhaling airborne pathogens Disease vector (insect, tick, etc.) Do you know any examples? Disease vector (insect, tick, etc.) Do you know any examples?