提醒：点这里加小编微信（领取免费资料、获取最新资讯、解决考教师一切疑问！）
One Sunday in November 20-year-old Alani Murrieta began to feel sick and was diagnosed with the flu. But by Tuesday morning she was having trouble breathing and was spitting up blood. Her family took her to the hospital, where X-rays revealed pneumonia （肺炎） . At 3:25 P. M. on Tuesday, November 28—one day after being diagnosed with the flu—Murrieta was declared dead.
But what exactly is a “flu-related death”?How does the flu kill?The short answer is that in most cases the body kills itself by trying to heal itself. “Dying from the flu is not like dying from a bullet or a black widow spider bite,” says AmeshAdalja, an infectious disease physician at the Johns Hopkins University Center for Health Security.
“The presence of the virus itself isn’t going to be what kills you. ”
After entering someone’s body—usually via the eyes, nose or mouth—the flu virus begins hijacking human cells in the nose and throat to make copies of itself. The overwhelming viruses cause a strong response from the immune system, which sends billions of white blood cells and antibodies to get rid of the threat. Tcells attack and destroy tissue harboring the virus, particularly in the lungs where the virus tends to take hold. In most healthy adults this process works, and they recover within days or weeks. But sometimes the immune system’s reaction is too strong, destroying so much tissue in the lungs that they can no longer deliver enough oxygen to the blood, resulting in death. In other cases, it is not the flu virus itself that causes a fatal immune response but rather a secondary infection that takes advantage of a taxed immune system. Typically, bacteria infect the lungs. Abacterial infection in the respiratory tract （呼吸道） can potentially spread to other parts of the body and the blood, even leading to septic shock: a life-threatening, body-wide, aggressive inflammatory （引发炎症的） response that damages multiple organs, such as heart, brain or muscles.
In atypical season, most flu-related deaths occur among children and the elderly, both of whom are uniquely vulnerable. Because the immune systems of children are relatively naive, they may not respond in the optimal way. In contrast the immune systems of the elderly are often weakened by a combination of age and underlying illness.
Apart fromthem, those at the greatest risk of developing potentially fatal complications （并发症） are pregnant women, health care workers and people with certain chronic medical conditions, such as HIV/AIDS, and heart or lung diseases, according to the World Health Organization.
49.The main purpose of the first paragraph is to .
A.summarize the symptoms of flu
B.introduce the seriousness of flu
C.emphasize the complications of flu
D.explain the procedures of diagnosing flu
50.One reason for flu-related deaths is that .
A.the virus destroyed the lung directly
B. bacteria infect white bloodcells andTcells
C. the immune systemdoesn’t fight back when attacked
D.the secondary infection of the flu damages several organs
51.The underlined word “optimal” in Paragraph5 probably means .
A.most confusing
B.most careful
C.most favorable
D.most tolerant
52.What’s the best title of the passage
A.Howdoes the flu actually kill people?
B.Why does the body destroy tissue in the lungs?
C.Who is the most likely to be infected with the flu?
D.Which is the most effective way to prevent the flu?
提醒：点这里加小编微信（领取免费资料、获取最新资讯、解决考教师一切疑问！）
