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28

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 ...


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 ...


22

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 ...


18

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 ...


16

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 ...


16

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 ...


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 ...


12

This really depends on the environment, one study (listed below as reference 1) found that the Ebola virus can survive under ideal conditions on flat surfaces in the dark for up to six days - see the figure from the same publication. However, the virus is quite sensitive to UV radiation (see reference 2 for all the details) and most viral particles are ...


11

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 ...


11

This is too long for a comment, so I put this in here: The main reasons are sociological. From the data I have read so far, this outbreak (actually these are two independent outbreaks, one in West-Africa and another one -not connected- in the Democratic Republic of Congo) is not exceptionally deadly in terms of Ebola. The death rate is about 60% which is ...


10

They appear sick because they are sick, but with other, opportunistic infections. The "immune deficiency" part of AIDS means that the immune system is not functioning normally and, thus, is unable to protect them. Typical illnesses that are more found more frequently in AIDS patients are pneumocystis pneumonia and Kaposi's sarcoma.


10

Viruses and other disease causing organisms are usually in an ecological steady state in different organism, called a vector. When they start to infect another organism similar enough that they can reproduce, they may turn out to be more virulent or fatal than is optimal for the organism. The classic example is the case of influenza outbreaks, the flu ...


10

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 ...


9

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 ...


9

Alright, having read the citation linked, and doing a little poking of my own, here's my approach at an answer: Some human herpes virus infections may compete with HIV infection. Essentially, some strains (not the ones you normally think of) infect CD4 cells - the same cells targeted by HIV. These strains down regulate transcription in CD4 cells, which in ...


9

Adding to the other answers posted: Hemagglutinin (HA or H) - Helps the virus enter the cell by binding to sialic acid receptors on cell membrane. It then unfolds in a lysosome and fuses the viral and lysosome membranes. Neuraminidase (NA or N) - Helps the virus exit the cell by cleaving the terminal sialic acid residues at the progeny virus release.


9

Firstly, it's important to recognize that "plant viruses" do not exist. There are only "viruses that affect particular plant cells", or "viruses that affect a particular cell type". You'll see why in a moment. One of the structural components of many virus is its protein coat. Different types of biological molecules protrude from the surface of this ...


9

For some background, it is essential to know that Ebola is actually a group (genus) of ebolaviruses, each with different fatality rates. There are five known species of Ebola, and four are known to cause disease humans (WHO: Ebola virus disease; wikipedia). The known species of Ebola includes: Zaire ebolavirus (or just ebolavirus) Sudan ebolavirus ...


8

This article has some good information. It's certainly more than I want to know about warts. Isolated warts may remain unaltered for months or years, or a large number of new lesions may develop rapidly in a short period of time. The development of warts is not predictable. Approximately 65% of warts disappear spontaneously within two years. ...


8

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 ...


7

The organelle form in the same way they would if they were coded for by the host's genetic code, except in this case the virus uses its own genome to specify the type of organelle. The article you link to indicates this. The "systems" in the quote are in part the organelle that it needs A study of the giant virus’s DNA shows it to have over a ...


7

The two letters represent the type of hemagglutinin (H) and neuraminidase (N) present on the viral surface. Those are the major surface proteins of the influenza virus and therefore crucial for the immune response. From Immunology and Evolution of Infectious Disease HA and NA reactivities with antibodies define the subtypes of influenza A (Cox and ...


7

It may actually be curable, as shown by success stories involving the Milwaukee protocol in which the brain is effectively shut down to allow for the immune system to eradicate the virus. In most cases, however, it is fatal once symptomatic. Note that the Milwaukee protocol boasts an imporessive (sarcastic) survival rate of under 15%


7

HIV hides in a number of known cells and unknown cells. Although most of the damage of HIV is caused by its infection of shorter lived cells, long lived cells which it infects includes anything with adequate receptors including memory T cells, dendritic cells, macrophages and some glial cells too. These cells are found widespread in the body from tissues to ...


6

The processes that control the germline of metazoans (multicellular animals) are highly regulated compared to single cell bacteria and eukaryotes as well as plants. At this point there are no clear stories of gene transfer into a complex animal, though there are some for plants: "animals and fungi seem to be largely unaffected, with a few exceptions, ...


6

I don't know if this is a comprehensive enough answer, but viruses are taxonomically broken down into order (-virales), family (-viridae), subfamily (-virinae), genus (-virus) and species. This system was developed by the ICTV and is concurrently used with the Baltimore System. A lot of species contain variations called virus strains. There are two types, ...


6

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 ...


5

I would say no. Some HIV strains are X4-tropic and not R5 tropic. That means that the virus uses the CXCR4 coreceptor and not the CCR5 coreceptor for entry into the CD4-positive cell.


5

As mentioned in this question , Adeno-associated virus is often used for gene therapy. This is due largely to its predictability when injecting genes (1), however it is also used as it is not implicated in any human pathology. As it is a replication deficient/helper dependent virus, natural infection is much less likely. The human immune system does ...



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