Taken from Latin word virus, which means poison or toxin, a virus is an infectious agent that can not thrive, survive or reproduce without a host cell.
The first known virus was first discovered in 1898 by Martinus Beijerinck and termed the tobacco mosaic virus. Today there have been more than 5,000 different viruses identified and viruses are considered to be the most abundant biological unit on Earth. A virus can infect any life form and viruses have been identified in virtually all ecosystems on the planet.
The study of viruses is a branch of microbiology and is known as virology. All identified viruses consists of genes that are either formed from RNA or DNA. The posses molecules that transport genetic information. The genes are protected by a layer of fat that envelopes them while they are outside of a host cell. The shape of viruses can range from basic icosahedral and helical shapes, to more intense and complex forms. While the origin of viruses is still unknown, it is thought that that may have evolved from bacteria or perhaps from plasmids, which are pieces of DNA that can travel between cells.
There are many ways that a virus can be transmitted. In plants viruses are typically spread from plant to plant by the insects which feed upon them and then feed on another plant. In animals they can also be transferred via blood sucking insects. Not all viruses transmit disease, following is a comprehensive list of some infectious viruses and how they are spread.
The common flu virus is distressing but rarely is it fatal. The influenza virus is typically spread via sneezing and coughing.
Making big news of late is the N1H1 virus, which is also commonly termed the swine flu. The swine flu is spread through humans by coughing and sneezing and also by coming in contact with a contaminated areas and transferred by touching the eyes or mouth. The swine flu can not be transmitted via food and thus can not be transmitted via pork products. This viral flu is usually most contagious during the first five days, but may be contagious for as many as ten days. The N1H1 virus strain has taken a number of lives, and has been termed a pandemic. While not typically fatal, the N1H1 virus has claimed lives but most deaths were of individuals with underlying illnesses. For the general population, the N1H1 virus is not fatal, but can be to those with underlying conditions, small children and the elderly.
The most effective means f controlling the spread of contagious flu virus is by diligent hand washing, cover mouth when sneezing or coughing as well as, limit exposure to others if one feels ill.
HIV/AIDS is one of several viruses that are transmitted through sexual contact, contact with bodily fluids and or blood transfusion. To date there is no cure for HIV. The spread of HIV/AIDS occurs via sexual contact with someone already infected with HI/AIDSV. It can also be contracted by sharing needles and in much rarer through blood transfusions with infected blood. Today there are stringent testing procedures that have virtually eliminated the chance of becoming infected via blood transfusions.
There has been no scientific evidence that supports the spread of HIV/AIDS through water, air, or biting insects. There is no cure for HIV/AIDS though there are many medications that extend an individual life and it is no longer a definite death sentence. The best means by which to diminish the odds of contracting HIV/AIDS is through abstinence, monogamy and the practice of using safe sex methods at all times.
The two types of Herpes Virus identified to date are HSV-1 and HSV-2. There are eight specific varieties of herpes that can infect humans. They can result in a variety of infections that range from the common cold sores or fever blisters to chickenpox and shingles. The herpes virus has also been associated with various types of cancer and can result in inflammation of the brain.
There is no known cure for herpes and this virus will result in life-long infection. There are some medications that will limit outbreaks and the spread of the disease, but the most successful means of controlling the spread of herpes is by practicing safe sexual habits and limiting or ceasing any sexual contact during an outbreak.
Hepatitis B is a viral disorder that affects the liver and causes inflammation, vomiting jaundice and in rare occasions even death. It is believed that as many as one third of the world's population has been infected with this form of the hepatitis virus. Hepatitis is spread via contact with infectious blood or by contact with bodily fluids which contain blood.
Hepatitis C is thought to include approximately 21% of all reported cases and the CDC has estimated that as many as 3.9 million Americans are infected arnd carry the Hep C virus. There are too many known virus to accurately list and describe them all. While antibiotics do not combat virus there have been developments in antiviral drugs (vaccines) that seem to help, reduce or limit the spread of viruses. Read about Hepatitis A.
Staying current and up to date with available vaccinations is the most economical and the most effective means by which to prevent the spread of some infectious diseases. There have been many vaccinations developed, such as, the polio, mumps, rubella and measles vaccines which have undoubtedly saved countless lives.