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I went to the doctor today with my girlfriend, and the doctor said that she had a virus but doesn't know which one and she should let the infection heal with some rest.

The fact that the doctor didn't know what type of virus she has bothers me.

Do physicians/biologists not know all the different types of viruses out there? Is it not possible to identify all of them?

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    $\begingroup$ Identification of the virus will generally not help the doctor or the patient, just wasting time and money - I'm not sure there's many countries where there is an abundance of doctors and funding for healthcare that this wouldn't be a problem! :) If your Dr had suspected it to be a dangerous virus I'm sure they would have investigated further. $\endgroup$ – rg255 Dec 22 '15 at 11:33
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    $\begingroup$ I, for one, certainly cannot. And since viruses recombine and produce new and new variants on a much faster scale than humans do, there is no chance that we can identify all existing viruses in the near future (or ever). Practically speaking, there is an infinite amount of different possible combinations of viral components. $\endgroup$ – István Zachar Dec 22 '15 at 13:35
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    $\begingroup$ Physicians and biologists are two different groups of people. $\endgroup$ – immibis Dec 22 '15 at 21:00
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    $\begingroup$ As an aside, I would suggest giving the Ted talk "Whats left to explore?" a read/listen. Admittedly its intended for a non-technical audience and may be a bit dated (from 2012). Biological dark matter is the corresponding (rather sparse) wiki page. $\endgroup$ – user8915 Dec 22 '15 at 21:06
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    $\begingroup$ To give you a picture of how little we actually know about microorganisms, if you take a soil sample from your back yard you are guaranteed to discover new species of microbes. Someone did this several years back simply to gauge how many more species there are to discover and to his surprise every time he did this experiment he always discover new species. Think about that: always. He could not find any soil sample that only contained known species of microbes. $\endgroup$ – slebetman Dec 23 '15 at 8:27
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Do physicians/biologists not know all the different types of viruses out there?

No, Biologists don't know all the viruses that exist out there. There's a lot! We do know many of the ones infecting humans, though, especially the ones leading to the most common diseases.

The fact that the doctor didn't know what type of virus she has bothers me.

Without knowing any symptoms, your girlfriend likely had was some kind of influenza (flu), rhinovirus (cold), norovirus (diarrhea, etc) or respiratory syncytial virus (strong). That's just the most common virus infections. Identifying those is possible (see lab tests for norovirus or influenza), but it's unnecessary in most cases.

The thing is, no matter which of these she has, the medical advice will stay the same - rest and fluids. So identifying them is just going to add time and money.

There are some cases where viral identification is done even for these diseases. For example, before giving an antiviral like Tamiflu, which is for example given to pregnant women with the flu. Before giving an antiviral, it should be established that she is indeed infected with the influenza virus. These tests are also done in patients who are hospitalized. In some countries and years, all influenza cases are screened to later know what strains of the virus infected how many people and how it spread.

As an example, if the result of the test doesn't change the treatment, the influenza test is recommended against by the CDC. With a gastrointestinal issue where norovirus is suspected, nobody is going to make an identification for a straightforward case.

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  • $\begingroup$ +1 for "There is a lot". It seems that the virus diversity of the oceans is more or less known now, at around ~5500 species: Scientists Map 5,000 New Ocean Viruses. (Most?) of these are not infectious for humans though. $\endgroup$ – David Tonhofer Dec 22 '15 at 18:32
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It's a cost/benefit situation. Yes they could have taken samples, processed them, teased out the virus, and eventually identified exactly what virus (sort of*) that your girlfriend had by its gene sequence. But do you want to pay 10k-100k per virus to find that out, or just pay $20-100 and take some fluids and be fine.

I say sort of because viruses tend to mutate quite a bit. A great example is the influenza virus. There are many strains, with genotyping you can say this is H5N1 vs H1N1. But typically the result for a person is going to be "You have the flu. <Insert generic flu advice here.>"

There are some tests specific to families, again flu is a great example. Because the flu virus can be deadly to certain groups of people, and because it affects a lot of people, it's important to have a rapid test for it. I just got the test today, only took about 15 minutes, thankfully I do not have the flu.

But for what I will call everyday cold viruses, there's no need for advanced or rapid detection. And that's where you get the answer you got today.

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