78

Do they exist? Yes What are they called? Marilyn Roossinck calls them viral mutualistic symbiotes. She has an excellent review here. What are some examples? My personal favorite is GB-Virus C, or Hepatitis G, which appears to slow the progression of HIV using a number of different mechanisms: Box 1. Summary of the effects of GBV-C infection in HIV-...


70

You must tell facts from fiction; viruses need living cells to replicate because they do not have the molecular machinery at hand to generate energy and construct building blocks essential to life. So no, viruses cannot bring back the dead or revitalize dead cells. One thing that comes close to it are the so-called zombie ants. These ants have been ...


66

If this is a topic that really interests you, I'd suggest searching for papers/reviews/opinions written by Didier Raoult. Raoult is one of the original discoverers of the massive Mimivirus and his work will lead you to some truly fascinating discussions that I couldn't hope to reproduce here. The main argument for why viruses aren't living is basically ...


54

It doesn't. Viruses don't "know" anything. Mutations occur at random. Most of them don't do anything, or have a slight negative effect on the ability of the virus to infect and reproduce. However, there are billions and billions of viruses. Once in a while a random mutation will offer a significant advantage like immunity to an anti-viral drug. The viruses ...


49

Many important viruses are coated with a lipid envelope and rely on this to enter the host cell. This envelope is fragile - it's similar to a soap bubble - and it can be disrupted in many ways. Lipids will oxidize in air over time and this will degrade their ability to maintain an envelope. Surfactants such as soap or solvents such as alcohol will disrupt an ...


46

Can someone die of the common cold? No. The common cold is a clinical syndrome restricted to upper respiratory tract involvement. By clinical syndrome, I mean it is the constellation of symptoms (rather than the consequence of a specific pathogen). As you mention, these symptoms are the result of the immune response, rather than tissue damage or ...


44

The CDC has made available online its nCoV test kit. Briefly,the kit contains primers and probes for real-time reverse-transcriptase PCR, as well as instructions for appropriate use and (critically) controls and guidelines to avoid false positives and negatives. Kits from different countries may use slightly different primers and probes, though since they ...


36

Long lasting immunity is obtained by means of the adaptive immune system, and mainly involves the development of antibodies that identify specific parts (epitopes) of the pathogen's proteins. Common cold is typically caused by a type of virus called rhinovirus. Viruses have very high mutation rates, which alter the sequence of the virus proteins, modifying ...


36

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. ...


33

HIV was identified as an infectious disease through classical epidemiology, and the virus was identified through classical virology. I won't get into the epidemiology, but briefly it went pretty much as you'd expect -- a cluster of symptoms were identified, patient characteristics were analyzed, the contagious nature of the symptoms were recognized, all ...


32

Mainly cost/benefit analysis. Using vaccines has a cost, both in dollars and in risk. That cost may be very low (cheap safe vaccines, like measles vaccine), or may be relatively high (smallpox vaccine is relatively risky, with around a 1 in 300,000 chance of moderate to severe side effects); but there is always some cost. Vaccines may not have any ...


28

It is possible for viruses to live in mutualistic relationships with their hosts, these associations are often overlooked due to the devastating effect that many viruses can have. To give an example in humans, when HIV-1-infected patients are also infected with hepatitis G virus, progression to AIDS is slowed significantly (Heringlake et al., 1998; Tillmann ...


25

Another good virus would be a Bacteriophage, a virus that infects and kills illness-causing bacteria. From Wiki: A bacteriophage also known informally as a phage, is a virus that infects and replicates within Bacteria and Archaea. The term was derived from "bacteria" and the Greek φαγεῖν (phagein), "to devour". Bacteriophages are composed of proteins ...


25

How long should I wait before handling the parcel to avoid contracting the virus? If you use gloves, or don't touch your face and just wash your hands after opening, you don't have to wait at all. If you don't use gloves or want to pick your nose, rub your eyes, or fiddle with your beard while opening the package, wait 24 hours if the package is nonporous, ...


24

The flu virus changes rapidly so that the current vaccine doesn't work against the new strains. The way vaccines work is that they teach our immune system what to look out for. The vaccine contains bits of the virus but in a form that can't cause a proper infection, the body learns what to look for and next time before the virus can really get going the ...


24

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 ...


23

This is because rabies is a viral infection of nervous tissue that propagates through peripheral nerves into the brain and causes brain tissue inflammation (encephalitis). As long as the virus is in the brain there is no way to get rid of it. The main trade-off here is that everything that would kill the virus will be as (or even more) aggressive against ...


23

First, I want to note that ddiez has a good answer, but I thought this was good question to have a more expanded answer on immunology and pathogenesis. The First thing we need to establish what is a "cold". The most common cold is rhinovirus (HRV), but the second place holder is a little harder to define. For example, respiratory syncytial virus (RSV) ...


23

Ultraviolet (UV) light emitted from the sun has enough energy to break chemical bonds in DNA and RNA. Some frequencies of UV light can cause damage in the DNA in skin cells that can lead to replication and expression errors, which lead to cancer (melanoma). Similarly, UV can break up and inactivate the genomic payload of a virus: Sunlight or, more ...


22

The sub-type is named for the broad classes of the hemagglutinin (HA) or neuraminidase (NA) surface proteins sticking through the viral envelope. There are 16 HA sub-types (designated H1 - H16) and 9 NA sub-types (designated N1 - N9). All of the possible combinations of these influenza A subtypes infect birds, but only those containing the H1, H2, H3, H5, H7 ...


21

It is only a question of definition. You can set the boundaries between living things and not living things anywhere. Some philosophers have argued that using a clear boundary between living and non-living things is not such a good solution. In nature, there would rather be a continuum from a stone to a bacteria. It is true that in thinking of viruses such ...


20

2019-nCoV is a virus that originated from the bat (at least this is the current hypothesis). It shows 96% squence similarity to the BatCoV RaTG13 sequence (see reference 1), showing its origin. It still is 87,99% identical to the "Bat SARS-like coronavirus", which explains the hit you found and is not unexpected, as these viruses are very closely related (...


19

From the UK National Health Service: Flu viruses capable of being transferred to hands and causing an infection can survive on hard surfaces for 24 hours. Infectious flu viruses can survive on tissues for only 15 minutes. Like cold viruses, infectious flu viruses survive for much shorter periods on the hands. After 5 minutes the amount of flu virus ...


19

There are actually 3+ types of test kits widely used to diagnose diseases caused by viruses. We can check for the nucleic acid of the virus, the antigen of the virus that would cause an immune response or the antibody produced during the immune response of the patient. Since we've already got the whole sequence of the nCoV, the test kits normally used this ...


18

I would say that if any "good" viruses exist, they are already within us. Retrotransposons are genetic elements in our DNA that were likely ancient viruses and they move around from time to time either by excising themselves and moving somewhere else or by making a copy and inserting it somewhere else in the genome. Even though we are born with them, their ...


17

Subtype is denoted using the HxNy notation for the variant of hemagglutinin and neuraminidase. Strain names are specified as: [virus type]/[location of origin]/[sequential number of isolation]/[year of isolation] ([subtype]), such as "A/Alabama/AF2070/2010(H1N1)" Virus type would be A, B, or C for the various forms of influenza (influenza A being the most ...


17

I agree with the answers already given, these are the reasons that viruses are not considered alive. I want to point out though that this isn't an area you find 100% agreement on; there is a decent subset of biologists who do consider viruses alive. I would say - completely on the basis of personal observation - that virologists themselves are the group most ...


16

We have engineered a few good viruses to treat certain diseases Per my comment and response: The most current example (at this time and based on my recollection) is the virus we have engineered to treat a certain type of macro degenerative eye condition: Scientists Have Reversed Age-Related Blindness by Deliberately Infecting Eyes With a Virus There are ...


15

I found a book chapter for you here Quick summary: 3 hypotheses to Origin of viruses From pre-cellular world (virus first hypothesis) From reductive evolution of parasites (reduction hypothesis) From fragments of cellular genetic material (escape hypothesis) Drawbacks: virus require cells (to infect) so how can they come first virus do not look like ...


15

There are quite some different definitions of being "alive", but a common one includes the need to have responsiveness, growth, metabolism, energy transformation, and reproduction (found from the Encyclopedia Britannica). Viruses depend on host cells to do all this, so seen alone as a virus outside a host cell, they are not alive. There's another short, but ...


Only top voted, non community-wiki answers of a minimum length are eligible