【正文】 s occur in protein metabolism:l There is a diversion of synthesis away from somatic and circulating proteins such as albumin towards acutephase proteins. l Protein synthesis is also directed towards immunoglobulin production and there is increased production of lymphocytes, neutrophils and other phagocytic cells.l There is a marked increase in nitrogen losses due to tissue breakdown, which may reach 1015 gram per day.Nutrition and host defenceUndernutrition impairs host defence. Natural resistance to infection is lowered by alterations in the integrity of body surfaces, the reduced ability to repair epithelia, and the reduction in gastric acid production. In addition, with malnutrition, immunological abnormalities are found.Mineral metabolism and acidbase balanceMineral metabolism and acidbase balance are disturbed during acute infection. In general, sodium and water are retained, principally owing to the effects of increased levels of aldosterone and inappropriate secretion of antidiuretic hormone. During the convalescent period after acute infection, a diuresis may occur. Acidbase balance disturbance is mon. Causes include respiratory alkalosis following tachypnoea related to fever, respiratory acidosis and hypoxaemia associated with pneumonia, and metabolic acidosis associated with septicaemia.In acute infection these changes are mild and resolve promptly without specific intervention. However, in situations where infections are prolonged and resolution is slow, supportive care may be necessary, particularly with respect to managing nutritional deficits and electrolyte and acidbase disturbances.THE EPIDEMIOLOGY PROCESS OF INFECTIOUS DISEASE AND INFLUENCING Epidemiology process is the process of occurrence, development and oute of infectious diseases. Essential elements of epidemiologic process Sources of infectionDefinition sources of infection : Human beings and animals in which pathogens can survive, multiply and, excreted to the environment .l The endogenous mensals : skin and bowel mensals can cause disease in the host, either because they have been transferred to an inappropriate site (. bowel coliforms causing urinary tract infection), or because host immunity has been attenuated (. candidiasis in an immunopromised host). l The exogenous source: Many infections are acquired from other people. Patients: Acute, chronic, typical, atypical.Subclinical infections(poliomyelitis, viral hepatitis).Carriers: Acute, chronic, convalescent, healthy (typhoid fever).l Zoonoses : Infections can be transmitted from wild or domestic infected animals to man. Infection can be acquired in a number of ways: direct contact with the animal, ingestion of meat or animal products, contact with animal urine or faeces, aerosol inhalation, via an arthropod vector, or by inoculation of saliva in a bite wound. Many zoonoses can also be transmitted from person to person. l Environmental source: Most microorganisms do not have a vertebrate or arthropod host but are freeliving in the environment. The vast majority of these environmental organisms are nonpathogenic, but a few can cause human disease. Persontoperson transmission of these infections is rare. Some parasites may have a stage of their life cycle which is environmental (for example the freeliving larval stage of Strongyloides stercoralis and the hookworms) even though the adult worm requires a vertebrate host. Other pathogens can survive for periods in water or soil and may be transmitted from host to host via this route (see below): these should not be confused with true environmental organisms.Routes of transmissionl Endogenous infectionThe body39。 contaminated blood or blood products are transfusedD Mother to infant。 many infectious diseases have a characteristic fever.Clinical course of fever: A Effervescence: Climbing up of body temperature, may be gradual or sudden.B Fastigium (fullbrown stage): Body temperature maintains at high level for several days.C Defervescence: Body temperature e down suddenly (crisis) or gradually.Pattern of fever:A Sustained fever: Temperature 39oC and difference of temperature loC within 24 hours. (typhoid, typhus).B Remittent fever : The lowest temperature above normal and difference of temperature loC within 24 hours. (remission stage of typhoid).C Intermittent (septic) fever: Fluctuation of temperature between high fever and normal temperature (septicemia).D Relapsing fever: Fever for a few days alternating with normal temperature for a few days.E Undulant fever: fever fluctuates for weeks or months alternating with normal temperature.F Saddle type fever: There are interval of 1 day remission between two waves of fever for a few days (dengue fever).l Skin rash (eruption): Skin rashes are mon features of infectious diseases, and the ears, eyes, mouth and throat should also be inspected. The weight should be place on its pattern, distribution, time and order of appearance. For example, rash of chicken pox appears on fist day and rash of typhoid on sixth day。 typical and atypical. DIAGNOSIS OF COMMUNICABLE DISEASE Early diagnosis is useful for isolating and treatment of the patient. Confirming diagnosis should be based on history, clinical manifestations, epidemical history, and investigations.Clinical manifestationsInfectious diseases can affect any organ or system, and can cause a wide variety of symptoms and signs. Historytaking and thorough examination covering all systems is required and should aim to identify the site(s) of infection, and also the likely causative organism(s).Epidemiological historyA detailed history is taken with specific questions about epidemiological risk factors for infection. These are based on the sources of infection and routes of transmission discussed above.l Travel 。 petechia in epidemic hemorrhagic fever, vesiculopustula rash in herpes simplex, Zona, urticaria in hepatitis, eschar in