LR Question 9 Explanation, by LSATHacks
QUESTION TEXT: Birds and mammals can be infected with West Nile virus…
QUESTION TYPE: Most Strongly Supported
FACTS:
- Birds and mammals can only catch West Nile from mosquito bites.
- Mosquitos can catch West Nile only from biting animals.
- Humans can catch West Nile, but they can’t spread it to mosquitos.
- West Nile started in north Africa, and spread to North America.
ANALYSIS: It’s fairly strongly supported that there are animals in North America capable of spreading the West Nile virus.
West Nile virus is in North America, and humans can’t spread it. Mosquitos can’t spread it on their own, so something else is spreading it. We know that animals can help mosquitos spread the virus.
___________
- West Nile could definitely be common. Humans can’t spread the virus directly, but if enough animals spread West Nile it could become common among humans too.
- Hard to say. West Nile only spread to North America recently. So perhaps the virus is only present in New England, but the densest concentration of mosquitos is in Louisiana, where the virus hasn’t reached yet.
- The stimulus doesn’t mention symptoms. We have no idea if people can catch the virus and not show symptoms.
- The virus started in North Africa. But it might affect more people in North America. Perhaps it spreads easier here. We have no idea, really.
- CORRECT. This is probably true. Humans can’t spread the virus to mosquitos, and mosquitos are the ones that spread the virus.
It’s likely that an infected animal arrived, and spread the virus to mosquitos.
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Hmm, please do correct me if I’m wrong but here’s where I have a problem with answer choice E: I find that it’s not really fair, due to the ambiguity of the word “carry” in my opinion. I’m assuming they mean it couldn’t be “spread” by people in North America, which given the information in the stimulus, would be true. However, would we not say that an infected person carried the virus to North America if a person that was infected with the virus took a plane from Northern Africa to North America.? The person may not be capable of spreading it (at least by way of mosquito transmission, as the person above me pointed out) But, The person still has the virus. The person was in North Africa and brought it with them to North America. If you don’t call that “carried” then what does one call it?
That’s true, but I’d argue that you can make the common-sense assumption here (as you initially did) that to “carry” the virus to North America is to be the person or thing responsible for the spread of that virus in the continent. First, this is a much more commonly used sense of “carry” in the context of disease transmission, and second, the stimulus states that the virus was spread, which suggests that (E) isn’t referring to one instance of the virus, but the many instances of the virus that have spread across North America.
YES “ONLY”. GAH sometimes I’m just so stupid….I have the only CIRCLED in my text and low and behold I just overlook it. Thanks and will keep your advice in mind! FYI I’m at 174+ right now generally and some of these aren’t ones I got wrong but ones I just don’t like…I too am fascinated by this test haha. This one I did get wrong though!
Ugh ok the more I think about it, I suppose it is implied that the virus would need to be in mosquitos and birds to be spreading beyond humans even in my previous hypothetical scenario and I suppose that it spread and since it’s rare for humans to contract then E makes sense. :). Answered my own question :)
Actually, it’s because of the first sentence of the stimulus: “Birds and mammals can be infected….ONLY through mosquito bites.”
Humans are mammals.
I’ve noticed in your comments is that your thoughts tend to stray too widely from what’s written. It’s useful to imagine alternate scenarios, but you have to make sure you’re basing it on the information given and not contradicting or ignoring it.
Ugh again maybe reading into things too much, but it doesn’t say a human can’t spread the disease other ways… couldn’t it be spread via sexual transmission and/or blood transfusion?! I just feel that can’t be ruled out just as much as you’re saying it’s hard to say about B. I would be SO MUCH MORE COMFORTABLE with E if it said something like “most likely not”. I suppose that degree of uncertainty is covered in the question stem? Even so, I really don’t see how E is any less tenuous than B?