Although genetic mutations in bacteria and viruses can lead to epidemics, some epidemics are caused by bacteria and viruses that have undergone no significant genetic change. In analyzing the latter, scientists have discovered the importance of social and ecological factors to epidemics. Poliomyelitis, for example, emerged as an epidemic in the United States in the twentieth century by then, modern sanitation was able to delay exposure to polio Until adolescence or adulthood, at which time polio infection produced paralysis. Previously, infection had occurred during infancy, when it typically 9rovided lifelong immunity without paralysis. Thus, the hygiene that helped prevent typhoid epidemics indirectly fostered a paralytic polio epidemic. Another example is lyme disease, which is caused by bacteria that are transmitted by deer ticks. It occurred only sporadically during the late nineteenth century but has recently become prevalent in parts of the United States, largely due to an increase in the deer population that occurred simultaneously with the growth of the suburbs and increased outdoor recreational activities in the deer's habitat. Similarly, an outbreak of dengue hemorrhagic fever became an epidemic in Asia in the 1950's because of ecological changes that caused Aedes aegypti, the mosquito that transmits the dengue virus, to proliferate.The stage is now set in the United States for a dengue epidemic because of the inadvertent introduction and wide dissemination of another mosquito, Aedes albopictus.


It can be inferred from the passage that Lyme disease has become prevalent in parts of the United States because of which of the following?


The inadvertent introduction of Lyme disease bacteria to the United States

The inability of modern sanitation methods to eradicate Lyme disease bacteria

A genetic mutation in Lyme disease bacteria that makes them more virulent

The spread of Lyme disease bacteria from infected humans to noninfected humans

An increase in the number of humans who encounter deer ticks

考题讲解

此讲解的内容由AI生成,还未经人工审阅,仅供参考。

正确答案是 E。
这道题的答案是E,因为文章中提到了Lyme疾病是由鹿蚤传播的细菌引起的,所以当鹿蚤的数量增加时,人们就更容易接触到这种病原体。而文章中提到,Lyme疾病在19世纪末只是发生点状,但最近在美国的部分地区已经开始流行,而这种变化主要是由于郊区发展和户外运动活动,导致鹿群数量增加,从而使人们更容易接触到鹿蚤。因此,E选项中的“鹿蚤数量增加”是导致Lyme疾病流行的主要原因,所以选择E是正确答案。

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