Infectious disease

What are infectious diseases Tiny microbes such as bacteria and viruses which get into your body and multiply in large numbers Forces of nature or evil deeds Discovered around 1680 – Antoni van leeuwehoek Bacteria, fungi, protozoa, viruses, and prions (referred to them as animal-cules) Not a microorganism

Mechanisms of infection Factor one Virulence – the organisms ability to cause disease Factor two The number of organisms which invade the body Factor three Resistance – ability to fight off infection

invasion Invasion Inflammation – swelling and redness Toxins microorganisms invade tissue and release toxins As blood passes through infected tissues the toxins are picked up and distributed throughout the body Mo travels to a specific area of body (cns)……ZIKA virus

Resistance to infection Immune system White blood cells Macrophages Lymphoid tissue Two functions Engulfing and destroying agents Producing antibodies

resistance Neutrophils – type of wbc Mobile units formed in bone marrow Provide rapid and potent defense Surround and kill mo

resistance Macrophages Large slow moving Reside in bone marrow, liver, spleen, and blood Kill organisms surviving the neutrophils

resistance Macrophages Inflammation Macrophages with the wbc will kill off invading mo Pus – result of the dead macrophages and wbc

lymphocytes T cell B cell Form antibodies that attach to the surface of MO marking it for destruction Attack organisms directly T cell B cell

Types of infectious agents Bacteria viruses Simple, one-celled organisms Most are harmless Pass body defenses or normal defenses are weakened Pathogenic almost always cause infection Most numerous life form – not a mo Need a host to survive Either dna or rna Take over host control centers in the nucleus Make special proteins causing symptoms & replicate themselves

viruses 1930’s – electron microscope helped to better understand shape and complexity Spread through Direct contact Indirect contact Insect or animal bite Influenza virus

Types of infectious agents fungi parasites Non-green plantlike Cause about 30 diseases – mycoses Evolve slowly Skin, hair, fingernails Live and feed on another organism endoparasites – protozoans that live within the body (tapeworm) Ectoparasites – live on body’s surface (ticks, fleas, lice, worms)

Disease classification Type of organism causing the disease Organ system they infect Setting in which they occur Most common encountered involve Skin Respiratory system Gastrointestinal urogenital

Prevention & treatment Reduce exposure to infectious organisms Maintaining body’s natural defense system Using immunizations Better nutrition and sanitation