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Viruses are extraordinarily small organisms that replicate within other living organisms. These little pathogenic particles can infect just about anything living. Some viruses cause massive amounts of damage on its host. Just think of the affect of humans on the earth. Then, there are viruses that have little to no symptoms in the host. The main goal for many pathogens is to spread to a viable host to replicate. There are many ways a pathogen can transmit from one organism to another. A few ways a pathogen can transmit are through sexual transmission, direct or indirect physical contact, fecal-oral transmission and through the release of pathogens through the respiratory tract ("Virus Transmission in Detail"). Viruses are the most efficient pathogenic microorganism to spread amongst organisms and the hardest to fend off.
Viruses come in a few shapes and sizes, however; they all have a viral genome and a packaging structure. The viral genome may be either single stranded or double stranded of DNA or RNA. Capsids are protein shells of a virus that contain the genome of a virus. Capsids may be enclosed in an envelope (Sloncezewski 182- 207). An envelope is composed "of membrane from the host cell which the virion was formed" (Sloncezewski 187). Enveloped viruses have a different aptitude when it comes to transmission. Viruses infect almost all living organisms on the earth and transmission is the key to survival.
Viruses are very good at transmitting in organisms via vertical (from parent to offspring) or horizontal transmission (one individual to another). The human immunodeficiency virus (HIV) is retrovirus that can do both vertical and horizontal transmission ("Virus Transmission in Detail"). Retrovirus is a RNA virus that uses reverse transcriptase to produce DNA from genome. HIV virus transmits from parent to offspring by shared fluids and through breast milk feeding. HIV transmits itself to others in a population through sexual interactions and direct contact into the blood ("Virus Transmission in Detail"). Not all interactions of a virus are contained in a single species.
Some viruses can also transmit to multiple species; this allows the virus to have more than one host species. The flu virus has three hosts: Humans, pigs, and birds. Therefore, there is a wide array of strands and the ability of mutation to occur in a species rises. This also makes it harder to eradicate the virus. The flu virus symptoms are also relatively milder than that of the small pox virus. A human with the flu virus still maintains daily contact with other individuals and this increases the ability for the virus to spread. Unlike the flu virus, the only viable hosts for the small pox virus were humans and the contagious period was very short with harsher symptoms. Individuals with small pox were quarantined and were confined to bed. This made it easy for humans to eradicate the small pox virus with the use of vaccines.
In order to minimize the affect of viruses on the body, scientists have made vaccines. Vaccines are biological particle containing solutions that aid the immune system in response to a particular disease. For viruses, successful vaccinations spoil the attempt of spreading the virus to that particular organism. If a population has a great number of individuals vaccinated, this creates a shield around individuals not vaccinated (Sloncezewski 985-1016). The chance of an infected individual to come into contact and spread the disease to an individual not vaccinated is reduced when more of the population is vaccinated. This shield around unvaccinated individuals is called herd immunity (Sloncezewski 985-1016). Sometimes an organism may be infected with a virus, but the virus will lay dormant.
Occasionally when a virus enters an organism, it will not begin to self replicate. Instead, the virus will inject its viral genome into the host's genome (Sloncezewski 199-204). The organism will replicate and the DNA will replicate and spread among reproduced organisms until it is triggered. Once the Virus has triggered by conditions in the organism, the viral genome will separate from the host's genome and begin to replicate inside the cell to be transmitted. After many replications of hosts, there are multiple organisms that contain the viral DNA and this spread is undetected until virus begins to express itself (Sloncezewski 199-204).Viruses are the only pathogenic microorganism that can spread this way.
Some other pathogenic microorganisms are arguably just as good as a pathogen transmitter as virus. Bacteria are single celled organisms that cause an immune response in the hosts' cells. The bacteria replicate and trigger an immune response. An immune response to bacteria is more affective a faster that Viruses (Sloncezewski 182- 207). In Viruses, it may take 5-10 days after viral entering an organism for an initial response from the immune system. In some instances, 5-10 days is too late to begin a response and the virus is too potent for the host, but after 5-10 days the virus has already been in the contagious period to infect others (Sloncezewski 182- 207). Overall viruses have a higher tolerance for antiviral compared to any other pathogenic microorganism and its medical remedy drugs. Protista live in moist environments and require water to live and transmit itself efficiently. Majority of pathogenic protista are parasitic and obtain all nutrients from the hosts it is living within (Sloncezewski 985-1016). The symptoms of a protist on reduce the overall level of nutrition and health in its host and this is counter productive if the protist wants to live. The fungi are creative, and can grow on dead objects and body parts (Sloncezewski 985-1016). This allows them to grow in environments not susceptible for other pathogenic microorganisms; however, they can easily be eliminated with medical drugs.
Although a virus may be affected by medical drugs, the affect of medical drugs on other pathogenic microorganisms is far greater than that of a virus. Also, the virus is able to hide within a host undetected spreading. The virus is more adapt to transmitting itself efficiently, is the hardest to treat with drugs, and hardest to eradicate. All other pathogenic microorganisms are in the viruses' shadow.
Sloncezewski, Joal L. John W. Foster. Microbiology: An Evolving Science. 1st ed. W.W Norton
& Company,inc. 2009. Print.