1. Viruses Ch 19 – Lecture
Monday 12/2/13
Tuesday: Lab Quiz: Protists and Fungi
Wednesday: Lecture Quiz on Fungi
Thursday: LAB Exam
* Bring book and notes

2. Importance of Viruses
1. Agent of diseases
2. Vector of gene in biotechnology
– 30% of human DNA is viral
3. Agent of evolution or mutation

3. Smallpox viral disease
• Infectious variola virus cause maculopapular rash
• Transmission via respiratory droplets
• Cause macropuplar rash (not itchy) with permanent
scarring
• Transmission via respiratory droplets
• Humans are the only known host
• Eradicated 1979
• Russia and US have smallpox samples
• Can be used as a bioweapon
• Death occurs in 30% of cases due to respiratory
complications

4. Chicken pox and shingles
• Varicella zoster virus
• Virus dwell in sensory nerves
• Symptoms include rashes, fever, and general
malaise
• Adult form: shingles

5. Rabies (hydrophia)
• Viral need treatment in 3 days
• Zoonotic disease (spread by animals) that
cause encephalitis resulting in violence,
madness, and hydrophobia
• Virus causes nervous damage
• Delirium, coma, death
• Bats are likely rabies vectors

6. Herpes I
• Herpes I cause sores and blisters

7. Herpes II
• Cause genital blisters
• Mild and asymptomic in healthy adults
• Can be transmitted to newborn

8. AIDS
• HIV targets specific cells. HIV kills white blood
cells with CD4 antigen, primarily T helper cells
• T-helper cells are crucial in the activation of
other white blood cells
• T helper cells are generals. They organize
immune strategy.
• Death from AIDS is due to opportunistic
infections
– TB, PDP, Kaposi Sarcoma, toxoplasmosis

9. AIDS v HIV
• HIV positive:
• AIDS: T cell count is below 200 micro-liter

10. Common cold, influenza, SARS, Hanta
virus
• Cause respiratory problems

11. Hepatitis A
• Liver inflammation
• Transmitted primarily contaminated water or
food
• Infection occurs during childhood
• Cause liver damage
• Vaccine available 

12. Hepatitis B
• Blood transfusion/exchange
• Vaccine vacation 
• Can lead to liver cirrhosis (hardening) and
caner

13. Hepatitis C
• Transmitted via blood exchange
• Most cases are asymptomatic
• Can progress to liver cirrhosis and cancer req
requiring liver transplant
• No effective vaccine available

14. Warts and cervical cancer
• Caused HPV
• Can lead to cervical, ovarian, genital, and anal
cancers
• We all have had it
• Can transmit by casual contact 
• Vaccine available for 70% of cases called
Gardasil. You have to get it before you get
sexually active.

15. Ebola & Marbug
• Mortality is as high as 90%
• Cause shock due to loss of vascular integrity
and loss of coagulation
• Endemic and sporadic 

16. Structure of Viruses
• Viruses are NOT cells.
• Viruses are obligate intracellular parasites. They are
active or reproduce only when inside host cells
• Viruses consist of nucleic acid enclosed in capsid
(protein coat) and membranous envelope.
• Each virus has a host range, a limit number of host cells
that it can inflect.
– Herpes will attack only nerve cells, not muscle cells
– H1N1 can go from one species to another
• Viruses are smaller and simpler than bacteria,.

17. All viruses
• 1. Have RNA or DNA
• All viruses have protein shells or capsids.

18. Viral genomes
• All viruses have double or single RNA or DNA.
It can’t be both DNA and RNA. It is one or the
other.

19. capsid
• Protein shell that encloses the viral genome
• Functions: attachment to host cell protection
of genome
• Capsid of some virus is used as a vaccine to
induce immunity
– BHV, HPV, and polio vaccines

20. Membranes (some viruses)
• Some viruses have membranous envelopes
that surround the capsid which helped them
infect host cells
• Viruses acquire membranes from host cells.
• Host cell membranes allow viruses to escape
detection by host white blood cells.
• exocytosis

21. spikes
• Some viruses have spikes protruding from
their envelope (glycoprotein)
• Spikes help viruses attach to host cells
• H (hemagluttin) N (neuranidase) H1N1: spikes
are made of proteins H and N.

22. Bacteriophages: viruses that infect
bacteria
• Two types: lytic and lysogenic

23. Lytic (virulent phage)
• Upon entrance, virus directs host cell to
synthesize more virus copies.
• Capsid stays out. Only DNA or RNA goes
inside the host.
• Lytic cycle terminates in death of host cell.
• Virulent phage: a phase that reproduces only
by lytic cycle
• Virus only injects the genome into host
cells, not capsid

24. Lysogenic
•
•
•
•
Viral DNA is incorporated into the host DNA
Virus knows when host cell will die
Prophage: integrated viral DNA
Every time host divides, virus genome also gets
copied and viral genome is passed on to daughter
cells.
• Temperate phage: uses both lytic and lysogenic
cycles. HIV is temperate
• Does NOT kill host cell immediately