viruses what human diseases can you name that are caused by viruses?
TRANSCRIPT
Did you name:
The flu – INFLUENZA! Swine flu! HIV/AIDS? Smallpox? Chicken pox/shingles? Common Colds? Hepatitis? Measles? Warts?
Viruses come in different shapes
They infect animals, plants and bacteria
Bacteriophagee.g. tobacco mosaic virus in plants
e.g. influenza, HIV and small pox
How are viruses named? Named for the type of cells they infect
or the disease they cause. tobacco mosaic virus is found in tobacco; bacteriophages infect bacteria HIV (Human Immunodeficiency Virus)
damages the human immune system
How does a virus infect?
1. Lytic – enters host cell & copies itself. Then causes the host cell to burst & spread the virus.
2. Lysogenic – virus puts its DNA into the host’s DNA (provirus) and it gets copied every time the host cell divides. The infection may show up years later, when infected cells enter the lytic cycle together e.g. HIV
Can only reproduce by infecting living things!
Retrovirus (backward virus) Retrovirus - contains RNA instead of
DNA must copy nucleic acid backward (RNA
to DNA) to function, using reverse transcriptase
All retroviruses must be lysogenic. Example: HIV
Is a virus alive? Made of cells? Can it reproduce without a host? Do they all have DNA? Do they maintain homeostasis?
They are NOT alive!
HIV Attacks immune system –
no cure yet Sep 2009 vaccine in
Thailand reported 30% decrease in infection
Bone marrow transplant?
Develops into AIDS
Killed more than 25 million since 1981
Came from SIV in late 19th century
Small pox Emerged in human
populations about 10,000 BC. Evidence of smallpox on the mummified body of Pharaoh Ramses V of Egypt
1967 killed 2 million people
USA smallpox free in 1971, world smallpox free in 1980
Ways we defend ourselves
Non-specific defenses—not a one-to-one defense; can be physical or chemical 1st line—skin! Prevents pathogens from
getting inside. Body secretions (sweat, tears, saliva, mucus, oil) also help chemically and physically
2nd line—inflammatory response—swelling, fever, non-specific white blood cells (macrophages)