【正文】 scrub typhus.l Toxemic symptoms: When microorganism multiple in tissue, their productions and toxin are released into blood and cause a series of symptoms: general malaise, anorexia, muscle and joint pains, mental symptoms, even progress multiple organs failure.l Bacteremia: The presence of living organisms in the blood can occur in healthy people without causing symptoms.l Septicemia:Bacteria multiple in blood and produce toxin lead to a series of sympotoms above description. Septicaemia can be plicated by metastatic septic lesions in organs or tissues. Examples include pneumococcal pneumonia and meningococcal meningitis. Circulatory failure of the septic shock syndrome is the most dangerous plication of septicaemia and is caused by Grampositive, Gramnegative or fungal organisms. l Monocyticmacrophagic system reactio:Monocyticmacrophagic system proliferate, congest and lead to splenomegaly, hepatomegaly, lymphadenopathy.Clinical types: The clinical pattern can be classified into fulminant, acute, subacute, chronic。 infected medical equipment is reused。 There may be more serious defects in host immunity owing to disease or chemotherapy, allowing normally harmless skin and bowel flora to produce invasive disease.l Airborne spreadMany respiratory tract pathogens are spread from person to person by aerosol or droplet transmission. Secretions containing the infectious agent are coughed, sneezed, or breathed out, and are then inhaled by a new victim. Some enteric viral infections may also be spread by aerosols of faeces or vomit. Some environmental and zoonoses pathogens are also acquired by aerosol inhalation,.l Faecooral spreadA Foodborne faecooral : Human and animal faecal pathogens can get into the food supply at any stage. Raw sewage is used as fertilizer in many parts of the world, contaminating growing vegetables and fruit. Poor personal hygiene can result in contamination during production, packaging, preparation or serving of foodstuffs. In the western world, the centralization of food supply and increased processing of food has allowed the potential for relatively minor episodes of contamination to cause widely disseminated outbreaks of foodborne infection.B Waterborne faecooral spread is usually the result of inadequate access to clean water and safe sewage disposal, and is mon throughout the developing world. In wealthier countries it usually occurs in isolated outbreaks with a specific source.l Contagium Respiratory and digest tract infectious disease can be transmitted by direct transfer (usually in small children), by contamination of clothing or household items (usually in institutions or conditions of poor hygiene). Some parasite disease is infected by soil such as hookworm, Ascariasis.l Vectorborne diseaseMany tropical infections, most importantly malaria, are spread from person to person or from animal to person by an arthropod vector. Vectorborne diseases are also found in temperate climates, but are relatively unmon. In most cases part of the parasite life cycle takes place within the body of the arthropod, and each parasite species requires a specific vector. Simple mechanical transfer of infective organisms from one host to another can occur, but is rare. Some vectorborne diseases are shown in Table 2 Table 2 Infections transmitted by arthropod vectorsDisease Infective organism Vector Dengue Flavivirus MosquitoYellow fever Flavivirus MosquitoScrub typhus Rickettsia tsutsugamushi MiteRickettsial spotted fevers Rickettsia sp. Hard tickTickborne relapsing fever Borrelia duttoni Soft tickLouseborne relapsing fever Borrelia recurrentis Body louseLyme disease Borrelia burgdorferi Hard tickPlague Yersinia pestis FleaMalaria Plasmodium sp. MosquitoLymphatic filariasis Wuchereria bancrofti Mosquito Brugia malayi MosquitoOnchocerciasis Onchocerca volvulus BlackflyLeishmaniasis Leishmania sp. SandflyAfrican trypanosomiasis Trypanosoma brucei Tsetse flySouth American trypanosomiasis Trypanosoma cruzi Reduviid bugl Direct persontoperson spreadA Sexuallytransmitted infections,B Skintoskin contacting。 specific portal of entry. Microorganisms are also highly specific with respect to the organ or tissue they infect. For example, a number of viruses are hepatotropic, such as those responsible for hepatitis A, B, C and E and yellow fever. This predilection for specific sites in the body relates partly to the immediate environment in which the organism finds itself。 invasion after preliminary adhesion。 specific stable (measles, typhoid) or unstable(Flu.)immunity acquired。GENERAL CONCEPT OF INFECTIOUS DISEASESINTRODUCTIONInfection can involve any organ or system of the body and thus embraces all medical disciplines. In this chapter and introduction is given to the general aspects, epidemiology, diagnosis, prevention and treatment of infection as well as descriptions of individual infectious diseases.l Definition of municable diseases: The group of diseases caused by prion, virus, chlamydia, richettisa, bacteria, fungus, spirochete,parasite with municability and may lead to en epidemic under proper conditions. l Definition of infectious diseases: The diseases caused by all living pathogens including municable diseases and unmunicable diseases. The subject of infectious diseases closely related to many subjects, such as microbiology, immunology, parasitology, pathology, diagnostic, internal medicine and so on. The goal of studying infectious diseas