What are viruses?: Viruses are the smallest life-form existing, since they are not even a single cell. It is almost like they are not alive at all. They are small strands of DNA-like cell material. A virus consists mostly of RNA and cannot survive without host cells.
How do viruses infect cells?: Viruses are infectious microbes that can be inside or outside cells. They are little strips of DNA (or RNA) usually wrapped inside a tiny capsule. Viruses are not even a single cell, but are a tiny part of a cell, and thus they are much smaller even than bacteria. Viruses are not alive in the normal sense. They do not feed, nor do they generate energy or waste products. Viruses are effectively inert until they attach to a live body cell. But once they attach, they become alive in a sense. They enter the cell, breaking open the capsule, so that their inside contents of DNA or RNA strips enter the cell. Because this viral DNA looks like normal DNA, the cell starts to copy it like the cell does to ordinary DNA. In this way, the body cell is tricked into making many copies of the virus inside the cell. Eventually, the cell is killed and these newly created viruses are expelled into the body to infect more cells.
Examples of viruses: Viruses are a very common type of infectious disease. Many of the most common human diseases are viral. There are literally hundreds of viral conditions.
- Common colds: "rhinoviruses", not one specific virus, but a whole group of viruses that share the common feature that they attack the nose/throat/lungs and cause the well-known cold-and-flu symptoms. Some viruses include: adenovirus
- Flu (influenza): also a set of viruses, but more severe than cold viruses??
- HIV (causing AIDS): a retrovirus
- Poliomyelitis (Polio virus): a disease eradicated by vaccination.
- Mononucleosis: caused by the Epstein-Barr virus (EBV)
- Rabies: caused by a rhabdovirus, usually caught by an infected animal bite.
- Chicken pox: caused by the varicella zoster virus, a member of the herpes virus family
- Rubella (german measles): caused by the rubella virus, not usually harmful, except to a fetus when the mother gets rubella.
- Ebola virus: an extremely deadly virus
- Human Papillomavirus (HPV): about 20 types, many are STD's, some are implicated in cancers of the sexual and oral areas.
- Herpes virus
- Respiratory syncytial virus (RSV)
- Cytomegalovirus (CMV)
- Yellow fever: a tropical disease caused by flavivirus, carried by mosquitoes.
- Dengue fever: a tropical disease caused by dengue virus (4 types) and carried by mosquitoes.
Antiviral medications against viruses: Antiviral medications are a relatively new class of medications that are only for treatment of viruses. Prior to the discovery of antiviral medications, the treatment of most viral conditions was mostly supportive and symptomatic (i.e. treat the symptoms of the virus but nothing acting directly against the virus itself). Until recently, most antiviral medications were very problematic, and only used against extremely severe diseases such as HIV. However, newer antivirals have been introduced against the flu.
Antibiotics and viruses: Antibiotics simply do not work on viruses. Antibiotics work against bacteria and some parasites, but never against viruses. A virus is not a cell, but only a small strand of RNA material that hides inside other cells. A virus does not feed or reproduce like a bacteria, so cannot be attacked by antibiotics in the ways that bacteria can. If a doctor treats a virus, such as the common cold, with an antibiotic, the goal is not to treat the common cold itself. Rather, the antibiotic is being used preventively against bacterial complications of the common cold, such as a bacterial ear infection. Certain secondary bacterial infections seem to arise whenever the body is also fighting a virus, so antibiotics can help prevent bacterial complications of viruses. Nevertheless, the use of antibiotics to treat viruses such as cold or flu remains a controversy.
Vaccinations against viruses:
Vaccines can be successful against viruses.
There are successful vaccines against many viruses
including smallpox, chicken pox, measles, mumps, rubella, and others.
The body's immune system kills viruses by actually killing
the whole cell that is virus infected.
Virus vaccines teach the body's immune system how
to recognize specific virus-infected cells.
Unfortunately, some viruses are difficult to create
vaccines against, because they mutate,
and the body cannot easily recognize the newly mutated form.
Vaccination against the flu is only partially helpful because
there are so many strains of the flu.
Flu viruses mutate very often,
which explains why a new flu vaccine is needed
The HIV virus is also particularly good at mutating itself,
and has defied attempts to create a HIV vaccine as yet.
Similarly, vaccines against the most common viruses,
such as the common cold, remain elusive.
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