Viruses
Chapters 18 (pp. 334-46)

Viruses - What are they?

Components:

Nucleic acid (double or single stranded DNA or RNA)

Protein coat (capsid)

Viral envelope

Help virus attack host

 

Virus Reproduction

Generalized (cd: Activity)

Can only infect cells in its host range

Protein coat recognition (lock and key fit)

Insert nucleic acid in cell

Reprogram cell to produce virus particles

Emerge from cell


Phage reproduction (virus of bacteria)

Lytic cycle (cd: Activity)


Lysogenic cycle (cd: Activity)

 

Types of viruses

Bacterial virus

Plant virus

Animal virus

 

Transmission in Plants

Horizontal Transmission

 

 

 

Vertical Transmission

 

 

 


West Nile Encephalitis

Inflammation of the brain

Commonly found in Africa, E. Europe, W. Asia, Middle East

New to W. Hemisphere in 1999

83 cases reported in 1999, 2000 - all in New York City metro area

9 deaths in 1999, 2000

2001- first cases outside NYC area

 

 

Will you contract West Nile virus?

 

 


Human Immunodeficiency Virus (HIV)

Retrovirus

 

 

Reproductive cycle of HIV (cd: Activity)

 

 

 

What about Bird Flu (Avian Influenza)?

 


Avian Influenza


 



Does Bird Flu Spread Easily to Humans?
 

 

 


Countries with human cases


East Asia and Pacific (Cambodia, China Indonesia, Thailand Vietnam)


Europe and Eurasia (Turkey)


Near East (Iraq)


Why the Concern?!


Potential for pandemic


Conditions for start of pandemic:
 

 

 




Viral Changes Enhancing Human-Human Transmission


Reassortment



“Adaptive Mutation”
 


 


Emerging viruses

Not really “new,” result from:

Mutations of existing viruses

Spread from one host type to another (expanded host range)

Hanta virus: mouse - human from dust/feces

Dissemination of virus from isolated populations to others:

Habitat destruction

World travel, etc.


CDC - Centers for Disease Control

In Atlanta, clearinghouse for disease info.

 

That's It For Viruses!!!!