英语六级阅读备考：快速阅读练习(7)
<p> <span word="Passage">Passage</span> 7</p><p> <span word="HIV">HIV</span><span word="AIDS">AIDS</span></p><p> <span word="AIDS">AIDS</span> <span word="has">has</span> <span word="now">now</span> <span word="surpassed">surpassed</span> <span word="the">the</span> <span word="Black">Black</span> <span word="Death">Death</span> <span word="on">on</span> <span word="its">its</span> <span word="course">course</span> <span word="to">to</span> <span word="become">become</span> <span word="the">the</span> <span word="worst">worst</span> <span word="pandemic">pandemic</span> <span word="in">in</span> <span word="human">human</span> <span word="history">history</span>. <span word="At">At</span> <span word="the">the</span> <span word="end">end</span> <span word="of">of</span> 2004. 20 <span word="million">million</span> <span word="people">people</span> <span word="had">had</span> <span word="been">been</span> <span word="killed">killed</span> <span word="by">by</span> <span word="it">it</span>, <span word="and">and</span> <span word="twice">twice</span> <span word="that">that</span> <span word="number">number</span> <span word="are">are</span> <span word="currently">currently</span> <span word="infected">infected</span> <span word="with">with</span> <span word="HIV">HIV</span>. <span word="Barring">Barring</span> <span word="a">a</span> <span word="medical">medical</span> <span word="breakthrough">breakthrough</span>, <span word="it">it</span> <span word="could">could</span> <span word="claim">claim</span> <span word="the">the</span> <span word="lives">lives</span> <span word="of">of</span> <span word="some">some</span> 60 <span word="million">million</span> <span word="people">people</span> <span word="by">by</span> 2015. <span word="AIDS">AIDS</span> <span word="exerts">exerts</span> <span word="a">a</span> <span word="terrible">terrible</span> <span word="toll">toll</span> <span word="on">on</span> <span word="societies">societies</span>, <span word="crippling">crippling</span> <span word="their">their</span> <span word="economies">economies</span>, <span word="decimating">decimating</span> <span word="their">their</span> <span word="labor">labor</span> <span word="forces">forces</span> <span word="and">and</span> <span word="orphaning">orphaning</span> <span word="their">their</span> <span word="children">children</span>.</p><p> <span word="Nine">Nine</span> <span word="out">out</span> <span word="of">of</span> 10 <span word="people">people</span> <span word="living">living</span> <span word="with">with</span> <span word="HIV">HIV</span> <span word="are">are</span> <span word="in">in</span> <span word="the">the</span> <span word="developing">developing</span> <span word="world">world</span>; 60 <span word="to">to</span> 70% <span word="of">of</span> <span word="those">those</span> <span word="are">are</span> <span word="in">in</span> <span word="Sub">Sub</span>-<span word="Saharan">Saharan</span> <span word="Africa">Africa</span>. <span word="But">But</span> <span word="the">the</span> <span word="disease">disease</span> <span word="is">is</span> <span word="spreading">spreading</span> <span word="in">in</span> <span word="every">every</span> <span word="region">region</span>, <span word="with">with</span> <span word="fierce">fierce</span> <span word="epidemics">epidemics</span> <span word="threatening">threatening</span> <span word="to">to</span> <span word="tear">tear</span> <span word="through">through</span> <span word="countries">countries</span> <span word="such">such</span> <span word="as">as</span> <span word="India">India</span>, <span word="Russia">Russia</span> <span word="and">and</span> <span word="the">the</span> <span word="islands">islands</span> <span word="of">of</span> <span word="the">the</span> <span word="Caribbean">Caribbean</span>. <span word="The">The</span> <span word="statistics">statistics</span> <span word="are">are</span> <span word="sobering">sobering</span> <span word="in">in</span> <span word="some">some</span> <span word="Southern">Southern</span> <span word="African">African</span> <span word="towns">towns</span> 44% <span word="of">of</span> <span word="pregnant">pregnant</span> <span word="women">women</span> <span word="are">are</span> <span word="HIV">HIV</span> <span word="positive">positive</span>, <span word="in">in</span> <span word="Botswana">Botswana</span> 37% <span word="of">of</span> <span word="people">people</span> <span word="carry">carry</span> <span word="the">the</span> <span word="virus">virus</span>.</p><p> <span word="Immune">Immune</span> <span word="Assassin">Assassin</span></p><p> <span word="The">The</span> <span word="human">human</span> <span word="immunodeficiency">immunodeficiency</span> <span word="virus">virus</span> <span word="is">is</span> <span word="a">a</span> <span word="retrovirusa">retrovirusa</span> <span word="virus">virus</span> <span word="built">built</span> <span word="of">of</span> <span word="RNA">RNA</span> <span word="instead">instead</span> <span word="of">of</span> <span word="more">more</span> <span word="typical">typical</span> <span word="DNA">DNA</span>. <span word="It">It</span> <span word="attacks">attacks</span> <span word="the">the</span> <span word="very">very</span> <span word="cells">cells</span> <span word="of">of</span> <span word="the">the</span> <span word="immune">immune</span> <span word="system">system</span> <span word="that">that</span> <span word="should">should</span> <span word="be">be</span> <span word="protecting">protecting</span> <span word="the">the</span> <span word="body">body</span> <span word="against">against</span> <span word="itT">itT</span> <span word="lymphocytes">lymphocytes</span> <span word="and">and</span> <span word="other">other</span> <span word="white">white</span> <span word="blood">blood</span> <span word="cells">cells</span> <span word="with">with</span> <span word="CD">CD</span>4 <span word="receptors">receptors</span> <span word="on">on</span> <span word="their">their</span> <span word="surfaces">surfaces</span>. <span word="The">The</span> <span word="virus">virus</span> <span word="uses">uses</span> <span word="the">the</span> <span word="CD">CD</span>4 <span word="receptor">receptor</span> <span word="to">to</span> <span word="bind">bind</span> <span word="with">with</span> <span word="and">and</span> <span word="thereby">thereby</span> <span word="enter">enter</span> <span word="the">the</span> <span word="lymphocyte">lymphocyte</span>. <span word="HIV">HIV</span> <span word="then">then</span> <span word="integrates">integrates</span> <span word="itself">itself</span> <span word="into">into</span> <span word="the">the</span> <span word="cell">cell</span> <span word="sown">sown</span> <span word="DNA">DNA</span>, <span word="turning">turning</span> <span word="the">the</span> <span word="cell">cell</span> <span word="into">into</span> <span word="a">a</span> <span word="virus">virus</span>-<span word="generating">generating</span> <span word="factory">factory</span>. <span word="The">The</span> <span word="new">new</span> <span word="viruses">viruses</span> <span word="break">break</span> <span word="free">free</span>, <span word="destroying">destroying</span> <span word="the">the</span> <span word="cell">cell</span>, <span word="then">then</span> <span word="move">move</span> <span word="on">on</span> <span word="to">to</span> <span word="attack">attack</span> <span word="other">other</span> <span word="lymphocytes">lymphocytes</span>.</p>
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