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Influenza and Vaccines There is no specific cure for in

游客2024-01-04  34
问题                      Influenza and Vaccines
    There is no specific cure for influenza. Recommended treatment usually consists of bed rest and increased intake of nonalcoholic fluids until fever and other symptoms lessen in severity. Certain drugs have been found effective in lessening flu symptoms, but medical efforts aimed against the disease focus chiefly on prevention by means of vaccines that create immunity.   No drugs can cure influenza, but certain antiviral medicines can relieve flu symptoms. Available by prescription, these drugs provide modest relief, but only if taken on the first or second day of symptoms. The drugs amantadine (sold under the brand name Symmetrel) and rimantadine (Flumadine), both in pill form, work against hemagglutinin and are effective in treating type A influenza. Two other drugs inhibit neuraminidase and are effective against both type A and type B strains: oseltamivir (Tamiflu) is in pill form and zanamivir (Relenza) is an inhalant.   A flu vaccine consists of greatly weakened or dead flu viruses, or fragments of dead viruses. Antigens in the vaccine stimulate the patient’s immune system to produce antibodies against the viruses. If the flu viruses invade a vaccinated person at a later time, the sensitized immune system recognizes the antigens, produces the antibodies and quickly responds to help destroy them.   About 5 to 10 percent of people who receive a flu vaccine experience mild, temporary side effects, typically soreness at the injection site. Young children who have not previously been exposed to the influenza virus are most likely to experience side effects.   Flu viruses constantly change so different virus strains must be incorporated in vaccines from one year to the next. Scientists try to provide a good match between the vaccine and the most serious virus strains circulating at the time. But because it takes months to manufacture and distribute vaccines, decisions on their composition must be made well before the start of each flu season. Each February experts at the World Health Organization (WHO) recommend a vaccine composition to be used for the forthcoming winter in the Northern Hemisphere; a second recommendation is made in September for vaccines to be used in the Southern Hemisphere. Typically vaccines contain antigens from three virus strains, usually two strains from type A and one strain from type B.   According to the CDC, the success of flu vaccines varies from one person to another. In healthy young adults, the vaccines are 70 to 90 percent effective in preventing the disease. In the elderly and people with certain chronic medical conditions, the vaccines are less effective in preventing illness but help reduce the severity of an infection and the risk of major complications or death. Studies show that flu vaccines reduce flu-related hospitalization by about 70 percent and flu-related deaths by about 85 percent among elderly people.   The CDC recommends annual flu shots for people who are at high risk for developing serious complications as a result of an influenza infection.
(A) [■]This group includes all people aged 65 and older; people in nursing homes and other facilities that house people with chronic medical conditions; people with chronic heart, lung or kidney disease, diabetes, an impaired immune system, or severe forms of anemia; children and adolescents with conditions treated for long periods of time with aspirin (which makes them vulnerable to Reye’s syndrome) ; and women who will be in the second or third trimester of pregnancy during the influenza season.
(B) [■] Some doctors encourage individuals who travel to areas of the world where influenza viruses circulate to receive the most current vaccine.
(C) [■] Vaccination taken earlier can better protect the travellers from being infected by influenza in the epidemic areas
(D) [■] vaccination is more urgently needed particularly if they are at higher risk of complications   It takes the human immune system one to two weeks after vaccination to develop antibodies to the flu antigens. According to the CDC, the best time to get flu shots in the United States is between October 1st and mid-November—sufficiently in advance of the peak of influenza activity, which in the United States generally lasts from late December until early March.   Flu shots must be given annually for two reasons. First, antibody protection that is provided by the vaccine decreases during the year following vaccination. Second, vaccines created for pre-existing viral strains may not work against new strains; nor does an infection with one flu strain confer immunity to infection by another strain. [br] The word them in Paragraph 3 refers to______.
选项 A、dead viruses
B、antigens
C、invading viruses
D、antibodies
答案 C
解析 本题为指代关系题，考查考生是否具备认定代词与篇章中其他词语的指代关系的能力。题目问：代词them在文章中指代的是什么?正如上一题所说，疫苗中含有一些dead viruses，即antigens(抗原)；抗原的作用是刺激免疫系统产生antibodies(抗体)。根据原文“If the flu viruses invade a vaccinated person at a later time, the sensitized immune system recognizes the antigens, produces the antibodies and quickly responds to help destroy them(如果流感病毒以后侵入接种过疫苗的人，人体被激活的免疫系统能辨认抗原，产生抗体，迅速回 应来帮助杀死它们)”。根据上下文，them在句子中是指入侵的病毒，即C项的invading viruses。其他三个选项所说的分别是疫苗中的死亡病毒、抗原和抗体，都不符合原文，因此选C项。
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