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# Epidemiologist: Malaria passes into the human population whe

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Epidemiologist: Malaria passes into the human population whe [#permalink]  09 Dec 2018, 03:18
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82% (01:21) correct 17% (01:37) wrong based on 34 sessions
Epidemiologist: Malaria passes into the human population when a mosquito carrying the malaria protozoa bites a human who has no immunity. The malaria parasite can remain in the blood of an infected person for up to forty days. The disease cannot be passed from person to person, unless a non-infected person is exposed to the blood of an infected person. Theoretically, malaria could be eradicated in any given area if all the mosquitoes carrying malaria in that area are exterminated. If such a course of action is carried out at a worldwide level, then the global eradication of malaria is possible.

Which of the following, if true, suggests that the epidemiologist’s plan for eliminating malaria is not viable?

A. A person who is infected with malaria can infect a mosquito that is not carrying malaria, if that mosquito bites such a person.
B. Some strains of malaria have protozoa that have been documented to last more than forty days inside the blood of a human.
C. Malaria is still endemic in many parts of the world, and many health workers believe that the global eradication of malaria is not possible.
D. Some people in areas where malaria is rife have developed an immunity to mosquitos, yet they also show a higher incidence of genetic disorders such as sickle cell anemia.
E. Mosquitos in many developing parts of the world are responsible for passing on a variety of viruses to human hosts.
[Reveal] Spoiler: OA

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Re: Epidemiologist: Malaria passes into the human population whe [#permalink]  11 Dec 2018, 07:01
I understand that A is the best possible answer for this question but I am still uncertain about a logic here. If all malaria carrying mosquitoes are eliminated AND all infected humans and cured, how can malaria spread after that? I might be overthinking this, but this was the first thought after reading option A.
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Re: Epidemiologist: Malaria passes into the human population whe [#permalink]  12 Dec 2018, 17:10
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I do think you said the exact word: overthinking.

You start from the assumption that all mosquitos with already the malaria protozoa carrying with them can infect humans.

Now, is Mosquitos bite human = infection.

If you eliminate ALl the mosquitos on the planet malaria is gone.

But what if a person is infected already and then is bitten by a mosquito NOT infected. The result is that mosquito could pass the illness to other persons.

To eradicate malaria you should wipe out from the earth ALl mosquitos And ALL humans. Which is clearly impossible..

This weakens the argument, pointing out that eliminate ALL mosquitos will not solve the problem.

Hope this helps
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Re: Epidemiologist: Malaria passes into the human population whe [#permalink]  19 Jan 2020, 21:48
Officail Approach

It's very easy to misread the conclusion of this passage as "killing all mosquitoes would eradicate malaria." After all, that makes the most sense because who wants to be bitten by any kind of mosquito? However, the conclusion is actually more specific than that:

"If all the mosquitoes carrying malaria are exterminated"

In other words, only certain mosquitoes are to be killed: those carrying the malaria parasite.

Thus, this may already trigger in your mind a key question about the conclusion: what about the other mosquitoes that will still be alive?

(A) is the correct answer. The epidemiologist's plan is to kill only those mosquitoes that carry the malaria virus. However, all the non-infected mosquitoes will still be flying around and biting people. If a person is infected with malaria, then that means that they have the malaria parasite in their blood. So when a non-infected mosquito bites that person, that mosquito will now carry the malaria parasite and will be able to freely spread the virus to new humans it bites. In other words, answer choice (A) exposes a major flaw in the plan: killing only certain mosquitoes will be meaningless since the remaining mosquitoes are still able to transfer the disease from human to human. The cycle continues and nothing has changed.

(B) may be both confusing and tempting since it looks a lot like answer choice (A). However, (B) can ultimately be paraphrased as "there's only one way to pass malaria from one human to another: mosquito bites." In other words, this answer choice is just ruling out other possible transfer mechanisms, such as a non-infected person touching the blood of a person infected with malaria. So, this answer choice is really just giving us an interesting fact: only mosquitoes can spread malaria between humans. However, this does not attack the epidemiologist's plan specifically like (A) does. (A) emphasizes that there's still a way for an initially non-infected mosquito to spread malaria, which highlights the main flaw in the argument (not killing all the mosquitoes instead of just the ones currently with malaria).

(C) is tempting for two reasons. First, it says that malaria is "endemic" in many parts of the world, meaning that it's commonly found all over the planet. This makes it sound like it would be very hard to eliminate. However, just because eliminating malaria would be difficult doesn't mean it would be impossible. Secondly, it says that "many health workers" don't believe in the conclusion of the argument, which seems to be saying the conclusion isn't sound. However, this is just the opinion of a group of people. This answer choice therefore doesn't actually give us any kind of fact or evidence that the epidemiologist's plan won't work.

(D) is off topic. The argument is concerned with malaria and mosquitoes, but this answer choice is talking about a completely different disease (sickle-cell anemia). Furthermore, people who are "immune to mosquitoes" wouldn't be a concern to the epidemiologist since those people wouldn't be able to contract malaria from the mosquitoes anyways.

(E) is also off topic. The argument is specifically about eliminating malaria and not other viruses. This also doesn't explain why the epidemiologist's plan would not work.
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Re: Epidemiologist: Malaria passes into the human population whe   [#permalink] 19 Jan 2020, 21:48
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