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Viruses

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VirusYour head aches, your nose

is runny, and your eyes are watery. You also have a slight cough. But do not be alarmed. More than likely, you are suffering from the common cold.

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The common cold is caused by perhaps one of the smallest disease causing organism- a virus.

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They are not alive, they do not grow or respond the environment but they affect living things.

They are not plants, animals or bacteria. They may seem like they are living but they are not because they do not show all of the characteristics of life. They are parasites.

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Virus- Are tiny infectious particles that consist of genetic material surrounded by a protein coat.

A virus can spread from person to person so we classify it as infectious.Infectious: Relating to a disease that is spread primarily through contact with someone who already has the disease.

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Capsid- The protein coating that surrounds the virus.

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Virus reproduction

They can only reproduce inside living cells (host). They replicate by taking over the cell machinery of a host cells and forcing it to make more viruses.

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Host cell- is the cell that viruses infect in order to make copies.

Because a virus infects the host and can cause harm, we commonly classify it as a parasite.

Parasite- An organism that grows, feeds, and is sheltered on or in a different organism while contributing nothing to the survival of its host.

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Three types of viruses: a bacterial virus, otherwise called a bacteriophage (left center); an animal virus (top right); and a retrovirus (bottom right).

Viruses depend on the host cell that they infect to reproduce. When found outside of a host cell, viruses, in their simplest

forms, consist only of genomic nucleic acid, either DNA or RNA (depicted as blue), surrounded by a protein coat, or capsid .

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Some the most common known virus

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Bacteriophage- is a virus that infects bacteria. They are shaped like space ships.

A T4 bacteriophage injecting DNA into a cell.

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Let’s look at the video clip of viruses uses cells to make new virus.

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Animation of the Lysogenic Life Cycle of a Temperate Bacteriophage

Viral diseases are prevented by giving a vaccine that is made from weakened, dead or synthetic form of the virus.

Vaccine- a preparation of killed microorganisms, living attenuated (weaken or reduce) organisms, or living fully virulent organisms that is administered to produce or artificially increase immunity to a particular disease

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Who can name the disease that these viruses can cause?

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Different types of viruses

Type A influenza virus

Ebola virusCourtesy CDC

RotavirusCourtesy CDC

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Rota virus causes stomach discomfort, vomiting and diarrhea in small children and the elderly.

Ebola causes a deadly disease the causes the internal organs to break down and the ooze blood from your major orifices in your body.

Influenza virus causes the flu.

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Ebola 1976, Ebola-ZaireZaire [Democratic

Republic of the Congo 318 died 88% of deaths.

It occurred in Yambuku and surrounding area. Disease was spread by close personal contact and by use of contaminated needles and syringes in hospitals/clinics. This outbreak was the first recognition of the disease.

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Ebola is a level 4 pathogen. The most deadly disease causing agents known to man are classified as level 4. This virus is highly contagious but not airborne. The incubation period for Ebola is 4-16 days depending on the strand.

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Last known caseOn March 25, 2005, CDC’s patients died during an outbreak of suspected hemorrhagic fever (Ebola) in Angola, Africa (Ebola-Zaire) . 122 people died.

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Patients exposed to the Ebola virus.

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There are many viruses that are undiscovered. Many lie dominant in the rain forests. When humans invade the forests they unearth the virus. That’s why we continue to study the effects of viruses in humans. This field of study is called Virology. It is very important work. Maybe one day some of you will work to provide a cure to some of the diseases caused by viruses.

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Let’s turn to page 27 C. Draw the diagram on the paper provided. You may use colored pencil or makers to make it colorful.