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VIRAL
SHAPES
VIRUSES
There are presently 20 recognized families of
viruses that affect humans and/or animals
CLASSIFIED BY:
– By whether they contain DNA or RNA
– By structure
– Also by type of capsid and or envelope
Viral Vocabulary
The CAPSID = the protein
shell that encloses the (DNA
or RNA).
ENVELOPE may contain
material from the host cell
as well as the virus
Bacteriophage
Bacteriophage = A virus that
infects bacteria
Viral Replication
Lytic vs. Lysogenic
Lytic – “Fast & Furious”
4 Stages:
1. Penetration: DNA or RNA injected into host
cell
2. Biosynthesis: Virus has hijacked the host
cell uses it to make copies of itself
3. Maturation: puts the viral pieces back
together
4. Lysis: cell membrane breaks open and
releases virus
Lysogenic – “Slow & Steady”
Integration of DNA/RNA into hosts
bacterium’s genome (chromosome)
When virus copies itself – new genetic
material is copied also
– then it can convert to the lytic cycle
This is how viruses mutate
http://www.youtube.com/watch?v
=_J9-xKitsd0
http://www.youtube.com/watch?v
=TVLo2CtB3GA
DNA VIRUSES
The following are a few
of the more common
DNA Viruses
Adenovirus
Adenoviruses
Cause colds
Conjunctivitis ("pink eye")
HPV - Papillomavirus
Often causes warts
Warts may go away
spontaneously
Human genital warts
may become
malignant if they
last for a long time.
Herpesvirus
Seven different
species are known
to infect humans
– Including herpes
simplex virus
(HSV)
– Cytomegalovirus
(CMV)
– Zoster (VZV); and
– Epstein Barr virus
(EBV)
Hepatitis B Virus
Hepatitis B
Can be acute or
chronic
It can last for up to
several months in
acute infections
Many years (even for
life) in chronic
infections.
RNA Viruses
Influenza virus
Rotavirus
Intestine – causes
diarrhea, especially
in children.
The term "rota",
meaning wheel
Paramyxoviruses
measles
mumps
encephalitis
VIRAL CLASSIFICATION review
RNA or DNA
Retrovirus
single-stranded or doublestranded
shape
enveloped or not
A couple of “strange bugs”
Hard to classify …
Rickettsia
These organisms are small
Pleomorphic (can change shape)
coccobacilli
Their structure similar to Gram-negative
bacteria
Rickettsia
Mycoplasmas
Mycoplasma are the smallest organisms
lacking cell walls that are capable of selfreplication
Seven different species infect humans
Pneumonia for example
H1N1
1918 Flu
Killer Flu
Spanish Flu
Killed somewhere between 20
– 50 million; infected 500
million
Viral Hemorrhagic Viruses
Ebola
Ebola hemorrhagic fever
The Ebola virus was first identified in
Sudan and in a nearby region of Zaire
(now Democratic Republic of the Congo)
in 1976.
Ebola is one of the most virulent (deadly)
viral diseases known to humankind,
causing death in 50-90% of victims cases.
Ebola
The Ebola virus is transmitted by direct
contact with the blood, body fluids and
tissues of infected persons.
Transmission of the Ebola virus has also
occurred by handling ill or dead infected
chimpanzees.
Ebola outbreak contained in Uganda
22 February 2008 (article from WHO)
In November 2007: the Ministry of Health
in Uganda confirmed an outbreak of Ebola
in Bundibugyo.
In all, 149 cases were detected and 37
patients died.
CDC – Ebola - Current
http://www.cdc.gov/vhf/ebola/index.html
Case Counts:
http://www.cdc.gov/vhf/ebola/outbreaks/20
14-west-africa/case-counts.html