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Viruses  Virus in latin means, “poison”  Definition- Infectious non-living particle that duplicates in the cells of an infected host. 2

Other definitions  Epidemic- A disease that is prevalently occurring in a small geographic area  Pandemic- A disease that is prevalently occurring over a wide geographic area  Vaccine- A preventative treatment used to provide immunity to a bacteria or virus  Eradicate- To get rid of completely  Antibody- Proteins created in blood and body tissue by the immune system to neutralize or destroy sources of disease. 3

Why don’t we call viruses living? They : 1. Are not made up of cells 2. Don’t eat 3. Don’t grow 4. Carry out biological functions (breathing) 4

5 A virus is surrounded by a capsid (protein coat) which determines the shape of the virus. The capsid contains nucleic acids (either DNA or RNA). Tail fibers for attachment to host cell.

Replication (making copies) 6 Viruses replicate in one of two ways:  Lytic- The virus invades the host cell and commands it to make new viruses, then the cell bursts and releases the new viruses.  Lysogenic- The virus invades a bacterial cell and merges its DNA with the bacterial cell’s DNA, then as the bacteria replicate, the virus is replicated.

Lytic cycle 7 Virus injects its DNA Virus DNA commands host cell to make new viral parts New viral parts assembled Cell lyses (breaks apart) and new viruses are released Virus attaches to host cell.

Lysogenic Cycle 8

9 DiseaseTransmissionSymptoms Common Cold Inhalation, direct contact Sinus congestion, muscle aches, cough, fever SmallpoxInhalationBlisters, lesions, fever, blindness, scars; often fatal Influenza (Flu) InhalationHeadache, muscle ache, sore throat, cough, fatigue, fever, chills WartsDirect contactLumps on skin or mucus membranes Tobacco Mosaic Virus Direct contact (of sap)Molting and discoloration of leaves Viral Diseases

Treatment  There are not cures for viral diseases  You can not treat a virus with antibiotics However…  Some viruses can be prevented through the use of vaccines. 10

Vaccines Vaccines contain weakened or killed strain of the virus weakened or killed strain of the virus 11 How Vaccines Work: 1. Weakened or killed virus enters the body (nasal spray or injection) 2. Your body responds to it by making antibodies. 3. Then, when your body comes in contact with the viruses later you don’t become symptomatic, you are immune.

What about Tamiflu?  Not a vaccine  Tamiflu targets a protein on the flu virus cells.  Normally, this protein helps the flu virus break through the cell walls so it can move on to other cells and replicate itself.  Tamiflu stops the protein from doing this, so that the virus can't leave the cell to infect other cells. 12

Example: Seasonal Flu Each seasonal influenza vaccine contains three influenza viruses. The viruses in the vaccine change each year based on international surveillance and scientists' estimations about which types and strains of viruses will circulate in a given year. About 2 weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body.  The "flu shot" — an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm.  The nasal-spray flu vaccine — a vaccine made with live, weakened flu viruses that do not cause the flu 13

What about 2009 H1N1?  Viruses are ever-changing  The H1N1 virus is basically a novel (new) strain (version) of the flu that humans don’t yet have any antibodies to.  Scientists have now isolated and created a vaccination for the 2009 H1N1 virus. 14