【正文】 16 ? In china, cases of 5327， death of 349 ? SARS: most serious emerging infectious diseases in 21 century 13 Emerging infectious diseases Avian influenza H5N1 virus H1N1 VIRUS 14 Antibiotics ? Antibiotics, within the last 60 years, ? Resulted in the cure of many previously lethal infections ? Only several years , drugresistant emerged. pathogenic staphylococci were found to have the ability to produce enzymes (penicillinases) that destroyed penicillin, thus rendering the drug useless against these strains ? Overuse and misuse make them useless. 15 COMMUNICABLE DISEASES INFECTION AND IMMUNITY PATHOGENESIS EPIDEMIOLOGY DIAGLOSIS TREATMENT PROVENTION PROFILE 16 CONCEPT OF COMMUNICABLE DISEASES ? Caused by pathogens: virus、 chlamydia、 richettsia、prion、 bacteria、 spirochete、 fungus and parasite（helminth、 protozoa） or medical insect ? Infectious disease: involve any an or system of the body and thus embraces all medical disciplines. ? Communicability which differentiates infections from noninfectious diseases. Transmission of pathogenic anisms to other people, directly or indirectly, may lead to an epidemic. 17 Infection and immunity 18 ? 一 . Concept of infection The course of struggle between pathogens and human or animal bodies (host). ? Absolutely necessary condition 19 ? Commensals ? opportunistic infection ? Primary infection ? Repeated infection ? Mixed infection ? Superinfection ? Secondary infection Kinds of infections 20 ? Commensalism Pathogens live in the host but don’t induce pathologic changes. Escherichia coli in the colon EpsteinBarr virus 21 ? Opportunistic infection: Pathogens within the host can induce pathologic changes if host immunity is suppressed by some factors. Cryptococcus neoformans Cytomegalovirus Candida albicans 22 ? Primary infection: measles, chicken box ? Repeated infection: malaria, schistosomiasis, ancylostomiasis ? Mixed infection: rare ? Superinfection: HBV overlap HEV ? Secondary infection: HBV following bacilli 23 ? Eliminate pathogen ? inapparent/subclinical infection ? apparent/clinical infection ? Carrier status ? Latent infection Infections status（ infection spectrum） Entrance and colonization of pathogens will lead to the following results 24 ㈠ Elimination: pathogens were excluded out by host nonspecific or specific immunity. Such as: Candida albicans Hepatitis A virus 25 ㈡ inapparent/subclinical infection: most frequently occurs in healthy individuals. The outes will be: A. Immunity acquired. HAV B. Carrier state: healthy carriers. HBV 26 ㈢ apparent/clinical infection : The outes will be: A. Recovery. Shigella B. Chronic carrier. Salmonella typhi 27 ㈣ Carrier state: Definition of different types of carriers: . incubation carrier . acute carrier . convalescent carrier . chronic carrier 28 ㈤ Latent infection: After infection, pathogens remain latent inside the body. Develop clinical manifestations when the host immunity has been impaired. Pathogens usually will not be excreted by the host during period of latency. Herpes simplex 29 ? The infection status may change each other in some conditions. Latent infection Apparent Carrier status Inapparent eliminate frequency/ratio 30 三、 Role of Pathogens in Infection Process: ⑴ Invasiveness: adhesion, peration ability. Shigella ⑵ Virulence: t