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? TTTThe main source of human disease pathogens is the human body itself. PPPPeople 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 VVVViruses take over a host cell’s genetic material and may cause death to the cells they invade BBBBacteria 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. WWWWhat makes us FEEL sick (fever, sore throat) are symptoms from our fight against the disease!
Patterns of Disease DDDDiseases are able to spread rapidly in today’s highly mobile world. EEEEndemic – a disease that is always present in a population. Ex. Common Cold EEEEpidemic – 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