IMMUNOLOGY THE NATURE OF INFECTIOUS DISEASE

How Are Diseases Caused?  Infectious diseases are caused by disease- producing agents called Pathogens. Bacteria, Protists, Fungi, and Viruses Bacteria, Protists, Fungi, and Viruses Not all microorganism are pathogenic Not all microorganism are pathogenic  Infectious disease – Any disease caused by the presence of pathogens in the body.

Where do diseases come from? TTTThe main source of human disease pathogens is the human body itself. PPPPeople can be carriers. They do not have the disease but act as a reservoir and can spread the disease.

Carriers  Carriers can pass on the disease during the incubation period.  Incubation period – A symptom-free period, while cells are multiplying within the body. Ex. Common cold, HIV Ex. Common cold, HIV

Other Reservoirs  Animals can also serve as reservoirs for microorganisms that cause disease in humans. Rabies Rabies  Soil and Water can be reservoirs for infectious disease. Soils can contain pathogens such as fungi and a type of bacterium that causes botulism. Soils can contain pathogens such as fungi and a type of bacterium that causes botulism. Water may be contaminated by feces Water may be contaminated by feces

Transmission  4 ways for pathogens can be transmitted from reservoirs to humans. Direct contact, by an object, through air or by a vector Direct contact, by an object, through air or by a vector  1. Direct contact – Common cold, Flu, STDs and HIV  2. An object – Food poisoning, food is contaminated by a food handler

Transmission  3. Vectors – An intermediate organism Insects and ticks: Insects and ticks:  Malaria is transmitted by mosquitoes  Lyme disease is transmitted by ticks  Fleas helped transmit the bubonic plague from rats to humans.

Causes of Symptoms of Disease VVVViruses take over a host cell’s genetic material and may cause death to the cells they invade BBBBacteria release toxins, which cause damage to the host. Toxins can produce fever, inhibit protein synthesis, destroy blood cells, or cause spasms Some toxins can be deadly. WWWWhat makes us FEEL sick (fever, sore throat) are symptoms from our fight against the disease!

Patterns of Disease DDDDiseases are able to spread rapidly in today’s highly mobile world. EEEEndemic – a disease that is always present in a population. Ex. Common Cold EEEEpidemic – occurs when many people in a given area are afflicted with the same disease at the same time. Ex. Flu, Polio

Treating Disease  Antibiotics are often used to kill or inhibit the growth and reproduction of bacteria  Produced naturally by various species of bacteria and fungi.  Do not affect viruses.

Problems with Antibiotics  Bacteria can often become genetically resistant to antibiotics. (This involves plasmid transfer)  Resistance is caused by continued use of antibiotics.  Penicillin first used in the 1940s but now after about 60 years of use, types of bacteria have evolved a resistance. The bacteria produce an enzyme that breaks down the antibiotic. Ex. Gonorrhea The bacteria produce an enzyme that breaks down the antibiotic. Ex. Gonorrhea