1. Pathogenesis of infectious disease

2. Path means disease
Pathogens refer to microorganism capable to cause a disease.
Pathology : the study of structural and functional manifestation of disease.
Pathologist : a physician who has specialized in pathology.
Pathogenicity : the ability to cause a disease
Pathogenesis : is the step or mechanisms involved in development of a disease

3. Phs in the corse of an infectious disease:
Incubation period: is the time that elapses between arrival of the pathogens and the onset of symptoms. And it is varies by many factor as health state-virulence of the pathogens- number of pathogens that enter the body.
Prodormal period: is the time during which patient feels out of sorts but not yet experiencing actual symptoms of the disease.
Period of illness: is the time during which the patient experiences the typical symptoms associated with that particular disease .(headache – sore throat-sinus congestion)

4. The convalescent period: is the time during which the patient recover.
Localized infection
Systemic infection
Acute infection : rapid infection followed out by rapid recovery (measles-mumps-influenza)
Chronic infection : slow insidious and last for long time
Symptoms of a disease: define as some evidence of a disease that is experienced by the patients.
( headache-fever-pain-itching)
Asymptomatic disease
Sign of a disease: define as some objective evidence of a disease that is experienced by the patients. (skin rash-enlargment of the spleen)

5. Latent infection : an old infection that was contained by the body but may re-activate at any time as ( ?) Primary infection: is the infection that the body get exposed to for the first time . Secondary infection : is an infection that follows a primary infection.

6. Step in the pathogenesis of infections disease:
Entry: of the pathogen into the body by: (Penetration, inhalation, ingestion and introduction of the pathogens directly into the blood. [shades needles]
Attachment: of the pathogen to some tissues within the body.
Multiplication: with local or system
Invasive / spread of the pathogens
Evasion of a host defenses.
Damage to host tissue (s). extensive or death.

7. Virulence:
is measure or degree of pathogenecitiy. different organism vary in their ability to cause disease some strain virulence some is a virulence.
Virulence factor: are the phenotypic characteristics of a microorganism that enable it to cause disease.

8. Structural features as pili ,capsule, flagella
Structural features as pili ,capsule, flagella. It help adhesion: which is molecule on the surface of the pathogens that able to recognize the reception on the host cell: that is glycoprotein molecule on the surface of the host cell that the adhesion on the pathogen attach to it.
Obligate intracellular pathogens.
Facultative intracellular pathogens.
Capsules: antiphagocytic by WBC. (No receptor).
Flagella: move and invade the aqueous area in the body it avoid phagocytosis.

9. Exoenzymes : is the two major virulence factors by which bacteria cause disease the exoenzyme as
(a) coagulase as in staphaurus: clot plasma → sticky coat → protect it from phagocytes.
(b) kinases: → streptococcus & stophausus: body produce fibricolt → kinases → lysis.
(c) hyaluronidase: enable organism to spread through connective tissue by breaking down hyaluronic acid.
(d) collagenase: Break down the collagen to invade tissue.
(e) hemolysins: damage RBC.
(f) lecithinase: damage extensive area of tissue.

10. Toxins: there are endotoxins that is integral part of the cell wall of the gram-negative bacteria can cause a number of adverse physiologic effect.
Exotoxins are the toxins that produced within the cells and then releases from the cell example:
Neurotoxins= that cause paralysis.
Enterotoxins = gastro intestinal disease.

11. Mechanisms by which pathogens escape immune responses:
The pathogens change their surface antigens example: influenze virus, HIV and nisseria.
The pathogen's surface antigens closely resemble host antigens and therefore not recognized by immune system = molecular mimicry.
Destruction of the host antibodies by producing enzyme as (IgA protease) that destroy IgA.