1. VIRUSES: Alive or Not?

2. RECALL: The SIX Characteristics of Life
Made up of cells
Made up of similar chemicals
Uses energy
Grows and develops
Responds to the world around them
Reproduces

3. The common cold virus - Rhinovirus
WHAT IS A VIRUS?
Virus: small, nonliving particle that invades and then multiplies inside a living cell.
Do not use energy to grow or to respond to their surroundings
Cannot make food, take in food, or produce wastes
The common cold virus - Rhinovirus

4. Virus Shapes and Sizes Vary in shape and size
Round
Rod-like
Robot-like
Brick shaped
Although they vary in size, all viruses are extremely tiny. The largest virus is no more than 250 nm long.
What’s a nanometer?

5. Virus Structure Protein Coat
- each virus has unique proteins on its coat, the shape of the proteins determine which cells it will attack.
2. Genetic Material
- Either DNA or RNA

6. Viruses Can Only Multiply When They are Inside a Living Cell
Viruses act like a parasite because they destroy the host cells they take over when they multiply.

7. Two Types of Viruses
Once a virus enters the cell it takes over the cell’s functions.
Some viruses take over right away, others wait a while.
Active virus
Hidden virus
Examples of each kind:
Hidden – HIV, herpes
Active – Rhinovirus, Influenza, Chicken pox

8. How Do Viruses Multiply?
                                                                                                      
How Do Viruses Multiply?
STEP ONE:
ABSORPTION
The virus attaches itself to the cell membrane

9. How Do Viruses Multiply?
STEP TWO:
ENTRY
The virus injects its genetic material.

10. How Do Viruses Multiply?
STEP THREE:
REPLICATION
The cell starts to produce the virus’s proteins and genetic material.

11. How Do Viruses Multiply?
STEP FOUR:
ASSEMBLY
New viruses assemble.

12. How Do Viruses Multiply?
STEP FIVE:
RELEASE
The cell bursts open releasing new viruses.

13. Hidden Viruses Multiply Differently
The only difference is that the hidden virus’ genetic material becomes a part of the organism for a while until it becomes active.
See the difference here.
Cep-1021

14. REMEMBER THE STEPS
ABSORPTION
ENTRY
REPLICATION
ASSEMBLY
RELEASE

15. Viral Diseases Can cause some short-term sickness (Ex. Common cold)
Can cause death (Ex. AIDS)
Spread through physical contact or inhaled droplets
NO medications to cure viruses.
medicines can treat the symptoms
Our immune system (white blood cells) is our first defense

16. Preventing Viruses
Vaccines: substance that stimulates the body to produce chemicals that destroy viruses or bacteria.
- may be dead or altered viruses
- they activate the body’s natural defenses

17. How are Antibiotics and Vaccines Different?
A chemical used to kill or slow the growth of bacteria
VACCINES
Virus introduced into the body in order to put the body “on alert.” If the virus ever infects the body, the immune system recognizes it and destroys it.

18. Why get a Vaccine? How are vaccines beneficial?
Besides vaccines, what other methods should be used to help prevent disease?
Why do people still get the flu even though they’ve gotten the flu shot?
Why not just get a SUPER Flu shot that covers them all?

19. EXAMPLES OF VIRUSES Polio Small pox Human Papillomavirus AIDS
Influenza
Herpes

20. How Viruses Effect Humans
HPV
More than 100 different strands
Transmitted by direct contact
Symptoms: Warts or none
Very extreme case:
Tree man

21. Measles – A Case Study
Symptoms: Measles symptoms usually show up in two stages.
Stage 1: runny nose, cough, and a slight fever. As the infection progresses, the person's eyes become red and sensitive to light, and the fever rises.
Stage 2 (3-7 days later) The fever reaches 103oF-105oF, and a red blotchy rash appears. The rash usually starts on the face and then spreads to the chest, back, and arms and legs,.The rash lasts for 4 to 7 days. Small white spots might also appear on the gums and inside of the cheeks.
Measles is very contagious. An uninfected person can get measles simply by breathing the air in a room where an infected person has been.
The virus can live in the air for 2 hours after an infected person leaves a room. Infected persons are usually infectious to others even before symptoms appear. (hidden virus)
Complications: Pneumonia occurs in up to 6 percent of reported measles cases and accounts for 60 percent of deaths from measles. Encephalitis (inflammation of the brain) can also occur.
Infants under age 2 years and adults over age 20 have a greater risk of complications.
Prevention: Get vaccinated!
Not so easy for some.