Viruses

“Bad News Wrapped Up In Protein”

When did we first learn about viruses?• First known in the

early 1800’s• 1935: Tobacco

Mosaic Virus -first seen under electron microscope

Viral Structure

A virus is a nonliving particle.

A virus is a strand of hereditary material surrounded by a protein coating.

The attack both plant and animal cells.

Some viruses can be:Active or Latent

Why are viruses not considered living?

Viruses must invade healthy cells in order to reproduce.

Viruses that infect bacteria are known as bacteriophages

Here one is injecting DNA Into a cell.

How small are viruses????

Viruses are so small that most can only be seen by the electron microscope ( 1935-tobacco mosaic virus)

17-300 nanometers long (one millionth of an inch) and about one thousand times smaller than bacteria

can only grow in other cells (host cells)

Tobacco Mosaic Virus

Adenovirus

Smallpox

Ebola virus

Why do we get infected with some viruses but not others?

• Each virus is specific for the type of cell (respiratory, intestinal, bacterial) that they invade because the receptor sites on the virus must match up with the receptor site on the host cell.

Example: Rhinovirus (cold virus) will only infect respiratory tissue

How do viruses multiply?

Viruses attack quickly and recruit the host cell’s enzymes to make new viral parts for more virus particles.

Once assembled, the

viruses will break free from the host cell which kills the host or pinching out from the cell membrane

Active Virus multiplies and destroys the host cell.

Latent- the virus injects its genetic instructions into the host’s genetic instructions. The virus remains “dormant” while the host cell undergoes cell reproduction. (provirus)

Example: cold sore on your lip.

Some environmental

or predetermined signal “stirs” the provirus to enter into the host cell.

HIV (Human Immunodeficiency Virus)

• HIV was first discovered in 1981

• HIV has killed 28+ million people worldwide

• Three million people died of AIDS in the year 2002 (that is the population of Chicago!)

• HIV is NOT transmitted by saliva, sweat or tears or insects

What do viruses do?

• In Animals: attack and destroy certain cells or cause cells to change function (can cause cancer)

Can’t be treated with antibiotics

Animal cells have NO cell wall to protect the cell.

How do viruses affect plants?

In Plants they do the same thing, but can also cause changes in color (such as stripes in tulips)

-Much more difficult to get into cells because of cell wall

What works against viruses?• Vaccines or immunizations By pre-infecting the body with small amounts of a particular virus, our body

can build up antibodies that will fight it for our lifetime

FIRST vaccine 1796 for smallpox. Edward Jenner

* Antibiotics DO NOT work against viruses.

PrionsMad Cow Disease• The word BSE is short but it stands for a

disease with a long name, bovine spongiform encephalopathy.  "Bovine" means that the disease affects cows, "spongiform" refers to the way the brain from a sick cow looks spongy under a microscope, and "encephalopathy" indicates that it is a disease of the brain.

• What Is BSE?

• BSE is a progressive neurologic disease of cows.  Progressive means that it gets worse over time.  Neurologic means that it damages a cow’s central nervous system (brain and spinal cord).

http://www.usatoday.com/money/industries/food/2003-12-24-mad-cow-qanda2_x.htm

For more information visit the following websites:http://www.fda.gov/AnimalVeterinary/ResourcesforYou/AnimalHealthLiteracy/ucm136222.htm