Download Virus Notes General Info Smallest of all microbes Can only

Virus Notes
I.
II.
III.
IV.
V.
General Info
A. Smallest of all microbes
B. Can only reproduce by replication in host cell
C. Tobacco mosaic virus first to be discovered in 1892
D. Have single or double strand RNA or DNA
E. If the attack bacteria, they are called bacteriophage
Structure (Bacteriophage)
A. Head made from protein membrane with 20 facets or sides surrounding DNA or RNA
B. Tail combines a collar attached to a tail sheath
C. Tail sheath surrounds hollow core
D. End plate with six tail fibers
Stages of attack (Bacteriophage)
A. Adsorption (attachment)- attaches tail fibers to specific cell-receptor sites
B. Penetration- enzyme called phage lysosome is secreted from tail, enzyme digest cell
wall, tail sheath contracts, and tail core penetrates, injecting RNA or DNA
C. Uncoating- Empty protein coat is left outside cell wall
D. Replication and nucleic acid replication- DNA or RNA takes over biosynthetic machinery
of cell; it directs cell to synthesize only phage DNA or RNA and phage coats or capsids
E. Maturation- phages continue to develop and phage nucleic material and protein coat
are being packaged to form mature phages
F. Release- Cell bursts or lyses to release new phages
Cell changes
A. Latent- no obvious damage at first
B. Cells may produce interferon
C. Rapid changes to genetic material (Ex: influenza)
Classifying Viruses
A. Classified by type of nucleic acid, by size and shape (morphology), replication typeand
by substructure of parasite
B. Poxvirus group- brick-shaped viruses containing DNA
C. Herpesvirus group- medium-sized, 20 sides containing DNA. Latent infections may occur
D. Adenovirus group- medium-sized, cube-shaped containing DNA (conjunctivitis)
E. Papovavirus group- small, cube-shaped viruses with circular DNA (warts)
F.
G.
H.
I.
J.
VI.
VII.
Myxovirus- medium-sized of helical form containing RNA (influenza)
Paramyxovirus group- similar to but larger than myxovirus (measles, mumps)
Rhabdovirus group- bullet-shaped viruses containing RNA (rabies)
Arbovirus group- arthropodborne viruses (carried by insects, ticks, and mites)
Picornavirus group- small, cube-shaped viruses containing RNA and divided into two
groups: enteroviruses (including polio) and rhinoviruses (common cold)
Facts and Myths
A. Facts
1. mothers can transmit HIV to unborn children
2. Women have higher risk of getting infected during heterosexual sex
3. Not all who have HIV have AIDS
4. Higher risk if engaging in unprotected sex
5. More resistant to disinfectants than bacteria
6. Hepatitis virus more resistant to heat than other viruses
7. Antibiotics do not help
B. Myths
1. HIV can be contracted from toilet seats
2. HIV is airborne
HIV virus
A. Human Immunodeficiency Virus
B. Retrovirus (single strand RNA that causes DNA to be produced)
C. Attacks CD4 T-lymphocytes
D. Incubation period (time from infection to actual development of disease) is 6 months to
five years (and sometimes up to ten years)
E. Progression
1. Flu-like symptoms about 7-10 days after infection
2. Only 1/3 get AIDS within 3 years
a. A (acquired)- not inherited or caused from medication
b. I (immuno)- refers to body’s natural defenses
c. D (deficiency)- lacking in cellular immunity
d. S (syndrome)- set of diseases that are present to signal diagnosis
3. Body seroconverts- blood tests reveal antibodies
4. CD4 cells reduce and symptoms appear
a. Candida albicans
b. Shingles (Herpes zoster)
c. Oral hairy tongue leukoplakia
d. Pneumonia (Pneumocystis carinii)
e. Karposi’s sarcoma
f. Mycobacterium tuberculosis
VIII.
Hepatitis- inflammation of liver
A.
B.
C.
D.
Fecal-oral borne are vowels (A and E)
Bloodborne are consonants (B, C, D)
Hep A- small RNA virus belonging to picornavirus class
Hep B- DNA virus belonging to the class hepadna- has an outer structure called
“hepatitis B surface antigen” and an inner core component called “hepatitis B inner core
antigen”
E. Hep C
F. Hep D- superinfects patients with Hep B because it has defective or incomplete RNA