Dr. Wael H. Mansy, MD Assistant Professor College of Pharmacy King Saud University Infectious Diseases

Study Objectives: to know 1.What is an infectious disease?? 2.What is an infection?? 3.Causes of re-emerging of the problem of the infectious diseases 4.Microbiological Classification of Infectious Diseases. 5.Means of Transmission of Infectious Diseases. 6.The action of pathogen in infectious process (pathogenicity) 7.What is infectivity,virulence, Immunogenicity and incubation period. 8.Manifestations of infectious process (Infection spectrum). 9.The immune reaction of host in infectious process. 10.Common symptoms and signs.

Infectious disease is :  A group of common diseases  Caused by different pathogens  Possessing infectivity.  To form epidemic.  Infectious disease is a threat to the health of people. What is an infectious diseases?? Infectious Diseases

A case is a risk factor …  Infection in one person can be transmitted to others What is an infectious disease?? Infectious Diseases

Definition of infection  Complex process of interaction between pathogen and human body  Infection is composed of three factors: pathogen, host and environment  There are commensalisms and opportunistic infection What is an infection?? Infectious Diseases

Causes of re-emerging of the problem of the infectious diseases: Infectious Diseases 1.Loss of Antibiotic Effectiveness. 2.Increased Population Density: Transmission from person to person is more likely. 3.Travel: Travelers may bring back pathogens. 4.Global Warming: May affect rainfall or other factors that currently affect diseases or their carriers. 5.Biological Warfare or Terrorist Attacks: There have recently been a number of threats of such attacks involving anthrax. 6.New Routes of transmission: Organ Transplants. 7.Complacency and Ignorance: Many, possibly most, people do not wash their hands after using the toilet.

BacterialGram-negative Gram-positive ViralDNA virus RNA virus Enveloped vs non-enveloped FungalDisseminated Localized ParasiticProtozoa Helminths Microbiological Classification of Infectious Diseases

ContactRequires direct or indirect contact (fomite, blood, or body fluid) Food or Water Ingestion of contaminated food or water AirborneInhalation of contaminated air Vector-borneDependent on biology of vector as well as infectivity of organism Perinatal Sexual Similar to contact infection, however, the contact may occur in utero or during delivery. transmission by sexual intercourse. Means of Transmission of Infectious Diseases

Factors Influencing Disease Transmission Weather Housing Geography Occupational setting Air quality Food EnvironmentAgent Host Age Sex Genotype Behaviour Nutritional status Health status Infectivity Pathogenicity Virulence Immunogenicity Antigenic stability Survival

The pathogenicity of pathogen is related to : 1. Invasiveness 2. virulent 3. Number of pathogen 4. Mutation (variability) Pathogenicity What does pathogenicity mean??? It means the ability of a microbiological agent to induce disease Infectious Diseases Factors Influencing Disease Transmission( Agent)

Infectivity:  Ability of agent to cause infection  Number of infectious particles required  In person-to-person transmission, secondary attack rate is a measure of infectivity Infectious Diseases Virulence :  Severity of the disease after infection occurs.  Measured by case fatality rate or proportion of clinical cases that develop severe disease. Factors Influencing Disease Transmission( Agent)

Immunogenicity  Ability of an organism to produce an immune response that provides protection against reinfection with the same or similar agent  Can be life long or for limited periods  Important information for development of vaccines Infectious Diseases Factors Influencing Disease Transmission( Agent)

Infection and Immunity Manifestations of infectious process (Infection spectrum): 1) Clearance of pathogen (no infection) 2) Covert infection (subclinical infection) 3) Overt infection (Clinical infection or apparent infection) 4) Carrier states  Health carrier after covert infection.  Convalescent carrier after overt infection.  Incubatory carrier before onset of disease. According to carrier time : #acute (transient) carrier #chronic carrier 5)Latent infection. Infectious Diseases

like smallpox  Direct tissue invasion: like smallpox produce toxins that invade and destroy tissue  Production of a toxin: anthrax produce toxins that invade and destroy tissue  Immunologic enhancement or allergic reaction  Persistent or latent infection  Enhancement of host susceptibility to drugs  Immune suppression Pathogenetic Mechanisms: Infectious Diseases

Cases  Index – the first case identified  Primary – the case that brings the infection into a population  Secondary – infected by a primary case  Tertiary – infected by a secondary case Transmission Infectious Diseases P S S T Susceptible Immune Sub-clinical Clinical S T

Incubation period  Time between exposure and onset of symptoms or signs of infection.  Each disease has typical incubation period but varies widely.  Requires replication of the organism to some threshold level for producing symptoms Infectious Diseases

 Tuberculosis  Scarlet Fever  tetanus  Gonorrhea  Diptheria  Streptococcal Infections  Pneumonia (can also be viral or fungal)  Pertussis  Bubonic Plague  There are many others. Bacterial Diseases

*Common Cold *Influenza *AIDS/HIV *Herpes (Simplex and Zoster) *Hepatitis A,B,C, D, E, F and G. *Measles, Mumps and Rubella. *Poliomyelitis. *Infectious mononucleosis. Viral Diseases

*Organisms, but without chlorophyll *Generally life off of dead organisms or dead material within a living organism. *Some are single cell organisms (yeast) *Some are multi-cell organisms (mushrooms) *Many are extremely valuable: -yeasts give us bread and alcohol -mushrooms. *Can cause disease by releasing enzymes that damage cells or by producing toxins. Some mushrooms produce VERY deadly toxins. Fungi

Fungal Diseases -Candidiasis. -Athlete’s foot - Tinea pedis -Jock itch - Tinea cruris -Nail fungus - Tineu unguis -Ringworm -Histoplasmosis -Over-the-counter medications are usually effective for mild infections, except of the nails. -Systemic treatments can be prescribed for serious infections, including the nails, and for histoplasmosis.

Fever:  Three stages : effervescence fastigium deffervescence  Five kinds of fever: *Sustained fever. *Sustained fever. *Remittent fever: one that shows significant variations in 24 hours but without return to normal temperature., *Intermittent fever: an attack of malaria or other fever, with recurring fever episodes separated by times of normal temperature, *Relapsing fever: alternating periods of fever and apyrexia, each lasting from five to seven days. *Saddle type fever. *Irregular fever. Common symptoms and signs Infectious Diseases

Mechanism of Fever Temperature is ultimately regulated in the hypothalamus. A trigger of the fever, called a pyrogen, causes a release of prostaglandin E2 (PGE2). PGE2 then in turn acts on the hypothalamus, which generates a systemic response back to the rest of the body, causing heat-creating effects to match a new temperature level.hypothalamusPGE2

A pyrogen is a substance that induces fever. These can be either internal (endogenous) or external (exogenous) to the body.internalendogenousexternalexogenous The bacterial substance lipopolysaccharide (LPS), present in the cell wall of some bacteria, is an example of an exogenous pyrogen.lipopolysaccharide Cytokines (especially interleukin 1) are a part of the innate immune system, are produced by phagocytic cells, and cause the increase in the thermoregulatory set-point in the hypothalamus. Other examples of endogenous pyrogens are interleukin 6 (IL-6), and tumor necrosis factor-alpha. Cytokinesinterleukin 1innate immune systemphagocytic cells interleukin 6tumor necrosis factor-alpha Mechanism of Fever

Rash eruption Date of eruption 1 st : chickenpox 2 nd : scarlet fever 3 rd : smallpox 4 th : measles 5 th : typhus 6 th : typhoid fever Location of eruption Form of rash Exanthema : *maculo-papular rash: A maculopapular rash is a flat, red area on the skin that is covered with small confluent bumps e.g. measles. *Petechia: *Vesiculo-pustular rash *Urtecaria. Enanthema Common symptoms and signs Infectious Diseases

 Toxemic symptoms  Mononuclear phagocyte system reactions Hepato- splenomegaly Lymph nodes enlargement  Clinical types acute, sub acute, mild, common, severe, fulminant, typical, atypical, abortive, ambulatory Infectious Diseases Common symptoms and signs