الفهرس 
EPIDEMIOLOGYOnly 14 pages are availabe for public view
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Abstract
Severe Acute Respiratory Syndrome (SARS) is an acute respiratory illness that hit the international community in the 21st century. SARS is a highly contagious severe atypical pneumonia, which had a very high mortality rate with overall estimate of case fatality ratio 14% to 15%. It originated in China in November 2002 and spread rapidly around the world. SARS-CoV, a novel coronavirus, was found to be the etiological agent of SARS in April 2003. The potential evolution of SARS-CoV in animals suggests that the disease may re-emerge in the future.
The condition appeared to be particularly prevalent among Healthcare workers and members of their household, indicating that the virus is predominantly spread by droplets or by direct and indirect contact of mucous membranes (eye, nose or mouth) and also through oral-fecal transmission. The infectious virus is present at very high concentrations in the respiratory tract of patients.
The clinical presentation of SARS is unspecific and the symptoms may resemble those of other forms of atypical pneumonia. Some features of the history, physical examination, radiological and laboratory findings, should alert clinicians to the possible diagnosis of SARS, even when the contact history is unreliable. The incubation period was estimated to be between 2 and 10 days. The illness usually began with high fever and mild respiratory symptoms but rapidly progressed to pneumonia within a few days. But fever may be absent during the early stages of the disease and in individuals with co-morbidities who may be impaired in their ability to mount a fever delaying the diagnosis of SARS. Fever is mostly associated with other symptoms including chills, rigors, headache, dizziness, malaise and myalgia. The clinical course of SARS is highly variable, ranging from mild symptoms to a severe disease with respiratory failure and death. The clinical course seems to be much milder and shorter among patients less than 12 years of age.
The duration of shedding of the SARS virus from respiratory secretions of SARS patients appears to be variable. The SARS virus may be shed persistently from the respiratory and/or enteric tracts of some humans without signs of disease. How long patients should remain in isolation depends on whether, and to what extent, patients continue to shed virus from the respiratory tract or from feces after overt clinical symptoms have stopped. At least SARS patients should limit interactions outside the home until 10 to 14 days after the fever and respiratory symptoms have resolved.
Nasopharyngeal swabs, throat swabs, stool, urine, lower respiratory tract specimens (sputum, endotracheal aspirate and broncheoalveolar lavage fluid) and blood specimens should be collected and placed into sterile containers. The likelihood of detecting infection is increased if multiple specimens are collected during the course of illness. Positive laboratory test results for other known agents that are able to cause atypical pneumonia, may serve as exclusion critiria. However, the possibility of dual infection must not be ruled out completely. Diagnostic samples should be suitable for viral culture, electron microscopy, antigen detection by PCR and serological antibody assays by ELISA, IF and neutralizing antibodies, also Immunological detection of SARS-CoV is available by monoclonal antibodies. Histopathology and cytological examination are also needed for the diagnosis. Detection of SARS-CoV antibody is considered the most reliable indicator of infection, since previous infection is still rare in most populations. During the course of illness, abnormal hematological values are common. Studies have shown lymphopenia and thrombocytopenia to be frequent in SARS patients. Common electrolyte and biochemical abnormalities include elevated levels of lactate dehydrogenase (LDH), aspartate and alanine aminotransferases and creatine kinase. A substantial proportion of patients demonstrate low calcium, phosphorus, magnesium, sodium and potassium levels.
Infection control measures for containment of SARS epidemic includes identifying and isolating suspect and probable cases and the management of their close contacts. To contain the spread of SARS-CoV all over the world, infection control in healthcare settings, in community and internationally is essential.
The best treatment strategy for SARS is still unknown. Since the outbreak, much work has been done testing new agents against SARS using in-vitro methods and animal models. The development of vaccines and new drugs for human use usually take many years. Antiviral therapy including ribavirin and corticosteroids were used extensively during the SARS outbreak, convalescent plasma and immunoglobulin may be beneficial. Interferons and empirical broad-spectrum antibiotics were routinely prescribed for SARS because its presenting features are non-specific.
The inactivated SARS-CoV vaccine may be the first vaccine available for clinical use because it is easy to generate; however, safety is the main concern. Other types of vaccines include S-Protein–based vaccines and vaccines based on fragments containing neutralizing epitopes. An ideal SARS vaccine should elicit highly potent neutralizing antibody responses, induce protection against infection and transmission; and be safe.