Prof. Qin Ning (宁琴), MD. PHD Department of Infectious Disease, Tongji Hospital,Introduction to Infectious Diseases,TONGJI MEDICAL COLLEGE HUAZHONG UNIVERSITY OF SCIENCE & TECHNOLOGY,What is an Infectious Disease?,Infectious Diseases - caused by human infection of micro-organisms and parasites Infection - the ability of an organism to invade and establish itself in a host Communicable Infection - a disease that is transmitted from person to another,What is an Infectious Disease?,Microorganisms Bacteria Virus Prion(盶毒体) Fungus Protozoa (原虫) Helminth (蠕虫) Products from microorganisms toxins,Current Situation,Increasingly serious threats from Communicable diseases Re-emerging: TB(结核), STD, plague(瘟疫), cholera(霍乱) Emerging: AIDS, SARS,The Incidence Rate of Communicable Diseases in China,Current Situation,The Proportion of Different Communicable Diseases by Etiology in China, 1950s-2002s,Transmitted by sex or blood,Gastrointestinal,Vector-borne and natural endemic,Respiratory,Leading Causes of Death,Reemerging Infectious Disease,Why? Human Demography and Behavior Technology and Industry Economic development and Land Use Microbial Adaptation and Change Breakdown of Public Health Measures and Deficiencies in Public Health,Natural Environment Destroy,Infection and Immunity,infection,immunity,Disease =,Response to Infection,adaptive immunity,Infection spectrum Primary Infection Repeated Infection Mixed Infection Superinfection Secondary Infection,Infection,Pathogen eradication,Overt infection Clinical Infection,Latent infection,Pathogen eradication,Carrier,Patient,Colonization,Carrier,Covert infection Subclinical infection,Bacteremia /viremia,Clinical Outcomes of Infection,Pathogenic effectiveness of micro-organisms,Pathogenecity,Invasiveness (colonization factor),Virulence (exotoxin and endotoxin),Quantity,Variability (HBV mutation),Immunity,Nonspecific immunity,Specific immunity,Natural barrier,Phagocytosis,Humoral factor,Cellular immunity,complement,cytokine,lysozyme,Humoral immunity,IgM,IgA,IgE,IgG,Immune Response in Infection Process,Cells of the Immune System,Leukocytes (Not Ag specific) neutrophils (PMNs) monocyte/macrophage eosinophil basophil Specialized cells (Ag specific) B-cells antibodies T-cells,T cells classification,How does the immune system work?,MHC class I molecule presenting an epitope,Infection and Immune,Infection and Immune (herpes simplex),Initial infection by herpes simplex virus in the skin is cleared by an effective immune response. But residual infection persists in sensory neurons. When the virus is reactivated, the skin is re-infected. This can be repeated endlessly.,Pathogenesis of Infectious Disease,Direct Injury Toxin Harmful Immune response,Invasion,Colonization,Output,Pathogen,Injury,Fever Metabolism disorder Endocrine disturbance,Development of infectious disease,Injury of cells and tissues,Disorder of pathophysiology,Adhesins Capsular material Proteins (Protein F, Protein M) Lipotechoic acids Fimbriae & Pili Endotoxins Gram negative LPS cell wall components (Lipid A and Core Sugars) Exotoxins Can be produced by either Gram Positive or Gram Negative Organisms,Cell and Tissue Damage Induced by Micro-organisms Bacteria,Cell and Tissue Damage Induced by Micro-organisms viruses,Direct attachment and killing Inhibit host cell synthesis (RNA, DNA, proteins) Intracellular replication and lysis Surface targets for host immune system Local direct damage leading to secondary bacterial infections Latent injury,Harmful Host Responses to Infectious Agents,Autoimmunity: break the rules of the “self-versus-nonself”. Direct against “self-proteins” Hypersensitivity reactions type I or immediate hypersensitivity (mast cell associated IgE) type II or cytotoxic hypersensitivity (antibody-complement activation and natural killer) type III or immune-complex-mediated hypersensitivity type IV or delayed-type hypersensitivity (activated T, CD8+, Mac) prolonged antigen exposure,Enterovirus Pathogeneis,Colonized herd,Epidemic Process,Epidemic Process,Source of infection,Route of transmission,Susceptible population,Why do people get sick?,New pathogens or changes in pathogens (HIV, Nile-like virus) Changes in environmental conditions (natural or man-made) Host Factors (Age, gender, ethnicity, immune status, Nutritional status, behavior),Source of Infection,Patient Covert infected person Carrier Infected animal,Other effective factors:,Climate Temperature, Humidity Society Sanitation, Cultural Background, War,Routes of Transmission,Air-borne, droplet infection,dust Fomite borne (污染物): Water, food, flies Direct contact of unclean hands and fingers, toys Vector borne A) mechanical B) biological Blood and blood source products Contact with soil Transplacental,HIVs Transmission Routes,Susceptible Population,A group of people at increased risk for infection and illness from a pathogen, often caused by a decrease in the effectiveness of th