1. Introduction to Virology

2. Virus Review Structure of a virus: How viruses cause disease:
DNA or RNA surrounded by a protein coat, called a capsid
Capsid allows for attachment to a host cell
A host cell is necessary for the virus to reproduce
How viruses cause disease:
Attach to a host cell, inject their genetic material, use the cell to reproduce, lysing the cell

3. Viral Specificity
Capsid’s surface markers determine what type of cells (what organisms) the virus can infect and what tissue(s) it can infect.
This is called the virus’ tropism.
May infect only one specific type of tissue or many different ones, but shape of the surface markers determine which cells is can attach to.

4. Virus Virulence
Viruses have genetic material that can encode for virulence factors to help them replicate and transmit more efficiently.
Loss of these virulence factors can result in viral attenuation
Attenuated viruses are “weakened” forms of the virus, usually unable to cause disease.
Lots of vaccines are attenuated

5. Steps in viral disease Acquisition: entry into the body
Initiation of infection at a primary site (tropism)
Incubation: Virus is attached but not necessarily enough to make you feel sick
May be asymptomatic (no symptoms)
May be symptomatic (generalized symptoms at onset called prodromal)
Symptoms caused by cells beginning to lyse in the area

6. Steps in Viral Disease cont.
4) Replication at target tissue
5) Convalescence: Immune response limits and contributes to disease
6) Resolution or persistent infection

7. Viruses are carried in the blood and lymphatics
If carried in the blood, its called viremia

8. Viral Infection
Manifestations of the viral disease are determined by the hypersensitivity and inflammatory reactions.
The relative susceptibility and severity of disease is determined by
Immune status, age, general health of the person
The viral dose
Genetics of the virus and the host.

9. Viral Transmission Direct contact
Injection with contaminated blood/fluids
Organ transplant
Airborne droplets
Depends on the type of tissue it infects

10. Viral Transmission
The presence or absence of a viral envelope is the major determinant of the mode of transmission
Non-enveloped viruses can withstand drying, detergents, extreme pH and temps.
Enveloped viruses cannot survive these
Non-enveloped= sturdy
Enveloped= fragile because they rely on the envelope to be intact in order to infect
Usually must remain wet (resp. droplets, blood, mucus)

11. Viral diseases that are carried in an animal are called zoonoses
Animals can act as vectors that spread viral disease and can be reservoirs for the virus
Viral diseases that are carried in an animal are called zoonoses
Specifically, many viruses are carried by insect vector…these are called arboviruses

12. Antiviral agents Get into your numbered groups.
You will be assigned a classification of antiviral agents
Design, on paper 1-3 powerpoint slides to explain your drugs/agents
Take turns on the computers, once approved, to create the slides. them to and be ready to present.

13. Laboratory Diagnosis
Patients symptoms and history provide the first clues to diagnosis
Usually you have to rule out bacterial and fungal infections first
There are laboratory methods that can confirm diagnosis

14. Cytology
Look for changes in cell morphology (any change in the normal cells is called a CPE, cytopathologic effect).
Common CPEs:
Syncytia= multinucleated giant cells caused by viral fusion of cells (HIV does this)
Inclusion bodies- cell structure changes

15. Electron Microscopy
Not a standard clinical lab technique