CHARACTERISTICS OF VIRUSES

Are Viruses Living or Non-living? Biologists consider viruses to be non-living because: Are not cells Do not grow or respond to their surroundings Cannot make food, take in food, or produce wastes Viruses do not respond to stimuli. They can only multiply if in another living cell

What are Viruses? Definition- Viruses are noncellular particles made up of genetic material and protein that can invade living cells.

Discovery of Viruses Beijerinck (1897) coined the Latin name “virus” meaning poison

Tobacco Mosaic Virus Wendell Stanley (1935) discovered viruses were made of nucleic acid and protein

Smallpox Edward Jenner (1796) developed a smallpox vaccine using milder cowpox viruses Smallpox has been eradicated in the world today

How Big is a Virus? Viruses are very small – smaller than the smallest cell.

Characteristics Non living structures Non-cellular Contain a protein coat called the capsid Have a nucleic acid core containing DNA or RNA (one or the other - not both) Capable of reproducing only when inside a HOST cell

Characteristics Some viruses are enclosed in an protective envelope CAPSID Some viruses are enclosed in an protective envelope Some viruses may have spikes to help attach to the host cell Most viruses infect only SPECIFIC host cells DNA ENVELOPE SPIKES

Characteristics Viruses cause many common illnesses/ diseases HIV VIRUS EBOLA VIRUS Outside of host cells, viruses are inactive Viruses cause many common illnesses/ diseases Some viruses may cause some cancers like leukemia Characteristics MEASLES

Characteristics Viruses cause many common illnesses diseases Some viruses may cause some cancers like leukemia MEASLES

What do Viruses look like? Viruses are unusual and different from other things in nature. Viruses come in a variety of shapes Some may be helical shape like the Ebola virus Some may be polyhedral shapes like the influenza virus Others have more complex shapes like bacteriophages

Types of Viruses: Helical Viruses

Polyhedral Viruses

Complex Viruses

Viral Taxonomy Family names end in -viridae Genus names end in -virus Viral species: A group of viruses sharing the same genetic information and ecological niche (host). Common names are used for species Subspecies are designated by a number

Used for Virus Identification Morophology RNA or DNA Virus Do or do NOT have an envelope Capsid shape HOST they infect

Herpes Virus SIMPLEX I and II

Adenovirus COMMON COLD

Influenza Virus

Chickenpox Virus

Papillomavirus – Warts!

HOST SPECIFICITY All kingdoms can be infected by viruses Viruses are kingdom specific but they may or may not be species specific Spread is specific to the type of virus

PARASITISM Viruses are parasites. A parasite is an organism that depends upon another living organism for its existence in such a way that it harms that organism.

Bacteriophages

Cylces Lysogenic Cycle Lytic Cylce Viral DNA May stay inactive in host for long periods of time Long lasting Example Mono or chickenpox Lytic Cylce Short and can be over come Example flu virus

Vaccine Is a weaken form of the virus To expose your immune system to the virus which will allow your body to better fight off the virus when exposed to the full blow virus.

Vector Control This is controlling the vectors that are carrying the virus. Examples: We stay home when sick, cover our mouth when we cough etc. We control the mosquito population in order to control the West Nile virus

copyright cmassengale Other Drug Treatments Specific to certain viruses. They don’t cure the virus but they can slow down and inhibit the multiplication of the virus. copyright cmassengale

Reducing the Risk They can’t be treated but they can be prevented! Cover mouth/nose when you sneeze of cough Wash hands frequently Avoid contact with the body fluids Not foolproof but reduces the risks