Viruses are microscopic particles that contain nucleic acid surrounded by a protein coat. They cannot replicate without infecting a host cell and hijacking the cell's machinery. There are two main viral replication cycles - lytic and lysogenic. Lytic viruses immediately take over the cell to produce new virus particles that burst and destroy the host cell. Lysogenic viruses integrate their DNA into the host cell which continues normal functions with the viral DNA. Some common viral diseases include influenza, HIV, hepatitis B, measles, rabies, and Ebola.

1. The deadly microscopic world.

2. • Nucleic acid within a protein coat
• Jenner – smallpox vaccine
• Non-living
• No metabolism
• Cannot replicate Influenza virus
without a host
• No scientific name,
instead family names

3. • Viruses that infect
bacteria –
Capsid
bacteriophage
protein
• General
Characteristics: DNA or
• Nucleic acid – either Tail
RNA or DNA RNA
• Outer protein capsid
• Optional features for
Tail fibers
protection
• Envelope,
spikes, slime
layers

5. • Prior to replication,
virus must enter cell
• Protein on virus
interlock with surface
markers on cells
• Each virus has specific
cell to “dock” with
• EX: polio virus
attaches to nerve cells

6. • Lytic • Lysogenic
1A. Virus attaches to 1B. Virus attaches to cell
cell 2B. Inserts DNA
2A. Inserts DNA 3B. DNA integrates into
3A. Replication of host DNA - prophage
viral parts 4B. Cell replicates normally
4A. Assembly of with viral DNA altering
new viruses protein synthesis
5A. Cell lyses 5B. Viral DNA comes out of
the host DNA
6B. Begin Lytic Cycle

12. • Inhibit protein synthesis of host
• Open lysosomes
• Bind membranes together
• Create a toxic level of proteins
The human body protects itself from
viruses using antibodies and fever. Viruses
prefer body temperature.

13. Which of these diseases is likely to be
caused by a lytic virus?
Characteristics of some Viral Diseases
Disease Symptoms Incubation
Measles Rash, Fever 9-11 days
Shingles Pain, itching on skin Years
Warts Bumpy area on skin Months
Influenza Body aches, fever, runny nose 1-4 days
HIV fatigue, weight loss, fever 2-5 years

15. Smallpox
• Last seen in 1977
• Eradicated by WHO due to obvious
symptoms and short life cycle
• CDC and Moscow
• Self-replicating

16. Chicken Pox
•Fluid filled blisters
•Itching and burning
•Common in kids
•Vaccine to
prevent

17. Herpes zoster –
shingles
•Reactivated chicken
pox
•Highly contagious
•Viral DNA remains
in neurons, dormant
•Pain, fever, skin
lesions, pus filled
spots
•Can be due to sun,
stress, fever,
trauma, but main
cause unknown

18. Untreated
shingles

19. Herpes simplex 2
• Genital herpes
• Virus lives in
bottom of the spine
• Same reactivation
• Congenital herpes in
newborns
• Tingling, pain during
urination, thick
discharge, fluid filled
vesicles
• Found in 25 mil
Americans

21. Cold Sores
•Herpes simplex
•Virus lives in a
nerve in face
•Reactivated
similar to
shingles
•Fever, sore throat,
mouth pain,
edema

22. Untreated cold sores

23. HIV
• Retrovirus RNA 
DNA
•Reverse
transcriptase
• Fluid transmission
• Enters immune
system by
endocytosis into
WBC
• Prevents WBC from
making a receptor
(CD4) that normally
detects pathogens

24. HIV
• Exposure symptoms –
headache, sore throat,
occasional rash
• Upon reactivation – rapid
weight loss, dry cough,
night sweats, unexplained
fatigue, white spots in
mouth, memory loss

26. Kaposi’s Sarcoma –
HIV side affect

27. Burkitt’s
Lymphoma
–
HIV Side
Affect

28. Rabies
• Virus lives in salivary
glands of animal
• Virus destroys the nerves
• Produces Negri bodies in
brain
• Initial symptoms –
tingling and cold around
bite, nervous
• Phase II – anxiety,
photophobia, arrhythmia,
pupil dilation, difficulty
swallowing
• Gamma globulin
treatment

29. Mononucleosis
• Fluid
transmission
• “kissing disease”
• Infects WBC’s
• Enlarged lymph
nodes,
swollen spleen,
sore throat,
nausea,
weakness, fatigue
• Can last up to 6
wks
• Remains latent in

30. Measles
• Highly contagious
• Respiratory droplet
spread
• Nasal discharge, dry
cough, fever,
headache, pink eye,
pink lesions, ear
infection
• Targeted for
eradication
• MMR vaccine

31. Viral Hepatitis B
• Initially
asymptomatic
• 1-3 month
incubation
• Fever, loss of
appetite, pain,
nausea, fatigue,
jaundice, swollen
liver
• 3 step vaccine

32. Hanta Virus
• Deermice and ticks
• No human to human
• 2-3 day incubation
• Cough, pulmonary
edema,
hemorrhaging, renal
failure, achy
muscles
• 60% death rate

33. Ebola
• 93% death rate
• Hemorrhagic fever
• High temperature
• Blood from orifices

34. Scott lives on a farm in the country. He started
feeling sick with flu-like symptoms. After a
couple of days, his pupils became dilated and
he had difficulty swallowing. His parents
rushed him to the emergency room. X-rays
revealed that Scott has small lesions forming
on his brain. He also had an animal bite on his
lower leg.
rabies

35. Mary is a 23 year old college student who went
to the doctor after several weeks of general
sickness. She complained of fatigue, chills,
sweating at night, a continuous cough, and
slight diarrhea. It was noted during the exam
that her glands under her arms and in her neck
were swollen. The doctors performed a blood
test.
HIV

36. A child, age 7, came home from school
complaining of a sore throat. Her mom took
her fever, which was 1020F. The child was
taken to the doctor after a couple of days with
no improvement. The doctor noticed that she
was developing a pink rash and seemed to
have an ear infection. She had not been
vaccinated with the MMR. What illness does
this child likely have?
measles

37. • Steroids given if severe – boost
immune function
• Usually cause fever
• Some vaccinations are weakened
forms of actual virus
• Many viruses stay in your system
even after recovery

38. A

39. B

40. J