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75

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-...


69

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 ...


61

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 ...


37

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. ...


35

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 ...


34

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 ...


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

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 ...


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

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 ...


23

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 ...


23

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 ...


21

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 ...


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 ...


19

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) ...


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 ...


18

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 ...


17

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 ...


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

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 ...


15

during the incubation period the virus is typically increasing in numbers and spreading between cells. It takes a while for symptoms to become obvious because it takes time for enough damage to be built up in the tissue to become noticeable. Take for instance the Rhinovirus which causes the common cold, once you become infected it is a day or so before ...


15

Interesting question and hard to answer definitively. First of all: It seems still pretty clear that the major (and by far most important) infection route comes from direct contact with infected people or their body fluids and that aerosol transmission is of far less significance. Ebola is infecting cells of the immune system (mostly macrophages and ...


14

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 ...


14

It's mainly caused by swelling of large veins and by an increase in vascular permeability that leads to an accumulation of fluids in the nasal mucosa. These effects are mediated, at least in part, by bradykinin and histamine, and can be counteracted by epinephrine. These mediators are part of the immune response to the viral particles. You can read more ...


14

This is now how new viral diseases are being named, possibly because one can have/carry a virus without having a disease (e.g. HIV, herpes simplex, etc.). It is not as uncommon as you think. A bit of googling will turn up reputable sites which discuss the epidemiology of Hantavirus disease, Hendra Virus Disease, Powassan Virus Disease, Lake Victoria ...


14

Edit: Matters Arising In this Nature News article, Scientists bust myth that our bodies have more bacteria than human cells, and in the bioRxiv pre-print article, Revised estimates for the number of human and bacteria cells in the body, a new estimate of the ratio of microbial cells on the human body to human cells that make up the body has been revised ...


14

You are not totally correct because these two strands don't have to be the same, they can be genotypically different, which occurs when a cell is infected by two distinct HIV strains. Also HIV uses reverse transcriptase which can "jump" from one strand to the other so sometimes pieces get repeated, skipped etc. So you will get a recombinant --> more genetic ...


14

The question title and the question itself ask two slightly (but critically) different questions. Can cancers caused due to viruses be contagious? NO Are these oncoviruses infectious in nature? YES The tumors caused by the viruses are not contagious. You can't take the tumor and transfer it to a new host and see a new cancer. The viruses that cause the ...


14

Cowpox and smallpox viruses structurally similar, and catching one confers immunity to both by immune system response, but one was a deadly disease and the other almost harmless. Once this was discovered, the days of smallpox were numbered. We had the means and the motivation to stamp it out. On my last check a few years ago, we are deliberately keeping ...


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