Viruses and Humans

Today’s Class• DNA and or Evolution Test Rewrite… DO ASAP!!!!• Report cards coming out in next couple of weeks… Your

chance to boost grade as much as you want before that

• We will get ONE more chance today to work on Virus Wanted Posters (Use time effectively)• We will be exploring the relationship between Humans

and Viruses

Where have we gotten so far…• We are now able to identify the different

components of a Virus• i.e. All Viruses have which two macromolecules?•Protein (Capsid) and DNA

• Some Viruses contain these two components:• An Envelope, and Glycoproteins

• There are different Viral shapes:• Helical, Icosohedral, Spherical and Complex

Where have we gotten so far…• Viruses must replicate using the cellular

process of a host cell• Viruses replicate in two ways (cycles)• Lytic and Lysogenic• The Lytic Cycle is what makes a virus “virulent”

– Disease causing• The Lysogenic cycle is what makes a virus

“dormant or temperate” – Becomes part of the host cell genome until a chemical inbalance causes Virus genes to go into Lytic cycle

Today’s Objectives• By the end of the class…• Name 4 different viral diseases that have

serious health impacts on humans• Compare two types of vaccines• Discuss the relationship between Viruses and

Cancer• Outline the Outbreak of a Viral infection

Let’s Play a Game of Viral v Non-Viral conditions…• On Whiteboard in front of you, write whether a

condition shown on the board is caused by a virus, or another type of pathogen (non-Viral)• One Point per right answer!

The Common Cold• VIRAL DISEASE

• Predominately caused by the Rhinovirus

Staph Infection• NON-VIRAL (BACTERIAL)

• Caused by Staphylococcus spp.

Malaria• NON-VIRAL

• Parasitic disease – Protozoan parasites in the genus Plasmodium

• #1 Cause of Human deaths throughout all of history

The Flu• Viral Disease

• Caused by the Influenza Virus

• Different strains cause different types of the Flu

Syphillis• NON-VIRAL

• Bacterial infection, caused by Treponema pallidum

Gonnorhea• NON-VIRAL

• Caused by the bacterium Neisseria gonnorhea

Cold Sores• VIRAL

• Caused by the Herpes Simplex Labialis Virus

Infectious Diseases• Many significant infectious diseases are caused by viruses which use

humans as their natural host• Some common Viral diseases we have likely encountered/heard of at some

point in our lives include (but are certainly not limited to) the following:• The common cold*• Influenza• Rabies• Small Pox• Chicken Pox• Mumps• Polio• Ebola*

The Common Cold• Predominately caused by the Rhinovirus (Though over

200 Virus strains are known to cause cold symptoms)• Why is there no current cure for the common cold?

• Upper Respiratory Tract Infection

• Symptoms are typically due to your bodies immune system

Of Course Viruses are known to cause more serious illnesses as well…

Viruses and Cancer (Table 25.3 in text)

• Cancer is a condition that results from uncontrolled reproduction of cells which invade surrounding tissue

• Cancer relates to genes that are mutated by outside agents (e.g. cigarette smoke, asbestos, sunlight, chemicals)

• Cancer genes can also be triggered by LYSOGENIC Viruses

• Ex. Hepatitis B (Liver Cancer), Epstein-Barr (Burkitt’s Lymphoma) Human Papillomavirus (HPV – cervical cancer)

Viral Outbreaks• Epidemic – Rapid spread of an infectious

disease, to a large portion of a population in a short period of time

• Pandemic – An epidemic of an infectious disease which expands across a wide region (sometimes world wide)• Who can think of a recent pandemic?

Ebola Outbreak 2014• Index case (Agent Zero) – A one year old boy from Guinea

(possibly bitten by a bat) died of Ebola and his family soon after. • *Custom of some west African tribes is to wash

themselves in water of the departed• Uhhhh….• Despite recommendations from WHO, this custom continued. • Nurses would go from village to village treating cases with

little protective equipment

• Fatality rates up to 70% at height of epidemic• Epidemic is still on-going in West Africa

Viral Treatment Options• Viruses are difficult to treat as their primary

method of reproduction mimics our own cellular processes• Despite this, scientific advancements have

allowed us to control and even prevent viral diseases/outbreaks from occurring

• Antiviral Drugs

• Vaccination

Anti-Viral Drugs• Not as many Anti-viral options out there as Antibiotics,

Antifungals or Anti-parasitic drugs.• There are still options available, and drugs being

researched right now…• Acyclovir – Used against Herpes Simplex and Chicken

Pox• Inactivates Herpes specific DNA polymerases without

affecting normal cellular processes

Anti-Viral Drugs•Azidothymodine (AZT) – Inhibits the Reverse transcriptase of retroviruses• Interfere with the synthesis of viral nucleic acids•Ex. Used against HIV

Anti-Viral Drugs•Protease Inhibitors – Interferes with the assembly of viral capsids during the replication stage of viral reproduction•Combinations of Protease inhibitors and AZT have been shown to slow the progression of the HIV infection (the lysogenic phase) to the AIDS (lytic phase)

Antibiotics•ARE NOT AN EFFECTIVE TREATMENT FOR VIRAL INFECTIONS•The prescription of antibiotics for viral infections (e.g. the cold and flu) have vastly increased the number of antibiotic resistant bacteria • In theory, if the trend continues, it could potentially spell extinction for the human race

Vaccination• A vaccine is a preparation of pathogens or other

materials that stimulates the bodies immune system to provide protection against that pathogen• Once your immune system has recognized a

pathogen, it has memory cells which will go into action and neutralize a pathogen if it ever infets your body again

• Viral vaccines consist of inactivated or attenuated viruses

Inactivated Viruses• “Dead” viruses – they are inactive, so they will

not replicate inside the host

Attenuated Viruses• Viruses that have been genetically altered so that they

will replicate, but are incapable of causing a disease in the host

• Attenuated vaccines are preferred, as the immune system builds greater protection, which lasts longer against these viruses

• Boosters: Extra doses of viruses which extend a persons protection against certain viruses

Vaccination Stats

Vaccination Stats

Vaccination Stats

The Very Best Way to Stop the spread of Viral Infections…

To Do Now• 15.1, 15.2 and 15.3 Review

• Chapter Review Questions in your textbook

• When you have completed 15.1- 15.3 Review show me, and I will give you a laptop to work on your Virus Poster