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*Resolution of symptoms (however, there are exceptions)-Fulminant presentation with little or no prodromal stage-Subclinical infection with no symptoms -Acute infections > evolving into chronic infectionCommunicabilityAbility to spread from one individual to others & cause diseaseMeasles, pertussis (easily spread)HIV (lower communicability)ImmunogenicityAbility of pathogens to induce an immune response InfectivityAbility of pathogen to invade & multiply in the hostPathogenicity Ability of an agent to produce diseaseSuccess depends on communicability, infectivity, extent of tissue damage,virulenceToxigenicity Ability to produce soluble toxins or endotoxins, factors that greatly influence the pathogen’s degree of virulenceVirulence Capacity of a pathogen to cause severe disease Measles= low virulence, rabies= high virulenceEndemicDiseases with relatively high (but constant) rates of infection in a particular populationEpidemicNumber of new infection in particular population greatly exceeds the number usually observedPandemicEpidemic that spreads over a large area (continent or worldwide)h.Differentiate between the structure, pathogenic properties and mechanisms by which bacteria, viruses and fungi cause disease. Organism StructurePathogenic PropertiesBacteriaProkaryotic unicellular microorganisms (no nuclei, mitochondria, membrane bound organelles)-Do not contain any organized intracellular organelles (have cytoplasm, ribosomes, lipid plasma membrane & outer rigid wall composed of peptidoglycan)Peptidoglycan is made up of sugar and peptides, provides protection against osmotic pressure, produced only by bacteria and site of action for -Some pathogenic bacteria cause diseaseunder certain conditions (Ie: entry through the skin via cut, sexual activity)-Strep & staph part of normal skin microbial, reside on healthy skin or nares- can initiate skin infections-May be treated with antibiotics
some antibiotics-Have single chromosome DNA coiled in center of cytoplasm, RNA functions to produce proteinVirusSmall pathogens, no organized cellular structures-Able to infect any cells including other microbes & viruses through one infected to one unaffected (direct or through a vector-mosquitoes)-Protein coat called a capsid that surrounds the nucleic acid core that is either DNA/RNA-Capsid responsible for protecting the nucleic acid & facilitates attachment of virus to host cell-Some have lipoprotein envelop that is derived from the host cell plasma membrane that they invade (HIV)-Do not have their own metabolism (unable toreplicate independent of the host), must incorporate their genetic material into that of host cells & force them to replicate)Life cycle: Attachment to target cell (determines host range), penetration (by endocytosis or membrane fusion), uncoating (release of viral nucleic acid from the viral capsid by viral or host enzymes), replication (synthesis of viral proteins and mRNA), assembly (formation of new virions), release (by lysis, budding)