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Virus
What is it?
Why are they important?
Dead or Alive?
Viruses are the smallest
of all “living”
organisms
Named after the
diseases they cause
Literally found
everywhere
Nonliving?
Viruses are considered
nonliving because
they do NOT exhibit
all the characteristics
of life. But they DO
reproduce.
Also, they require a host
cell to complete their
life cycle.
So What’s the Big Deal?
Number 1
Viruses always kill the host cell during
their replication
Number 2
Practically impossible to get rid of a
virus once it is in the body
So…
Syphilis
Herpes
Gonorrhea
And everyone’s favorite--HIV
Before you decide you are ready for a sexually
transmitted disease take a look at the following
pictures. Remember, you can treat the
symptoms, but you’ll always be sick.
HIV / AIDS
Herpes
Syphilis
Hepatitis
HPV / Genital Warts
And last but not least…
Ebola
This virus looks
harmless, but…
It can cause you to get
a headache, fever,
and diarrhea before
you start bleeding
internally and vomit
your internal organs.
Viral Structure
Protein Capsid (surrounds the nucleic acid)
Nucleic Acid (genetic information)
Lipid membrane (for protection)
Some have tails (for attachment)
Viral Structure
Viral Lytic Cycle
1. Attach to a host cell
2. Inject genetic material into host cell
3. Host cell replicates the viral genetic
material as it copies its own DNA
4. Newly formed virus parts are assembled
in the host cell
5. Newly formed viruses lyse (break) the
cell membrane and look for a new host
Beneficial Usage of Viruses
Cancer fighting virus called VSV kills the most
malignant form of brain cancer in mice.
A virus called NV1020, is a type of herpes
simplex virus modified so that it selectively
replicates in virus cells, killing them in the
process.
A mixture of six bacteria-killing viruses, called
bacteriophages, can be safely sprayed on meat
and poultry to combat common microbes that kill
hundreds of people a year
Vaccines
 Vaccines are dead or weakened pathogens (viral
material) that produce an immune response
when injected into a healthy person.
 They increase white blood cell production which
alleviate (lesson) some of the effects of a viral
infection.
 Most vaccines now contain no mercury, recently
thought to have a negative impact on a child’s
neurological development.
Recent Viruses in the news
West Nile Virus
 Transmitted via infected mosquitoes
 Minimal symptoms in most infected people
 Extreme cases lead to encephalitis
(inflammation of the brain) and meningitis
(inflammation of the lining of the brain and
spinal cord), both of which can be fatal
Avian Flu—H5N1
The reported symptoms of avian influenza in
humans have ranged from:
typical influenza-like symptoms (e.g., fever,
cough, sore throat, diarrhea and muscle aches)
eye infections (conjunctivitis)
Pneumonia
acute respiratory distress
viral pneumonia
other severe and life-threatening complications.