Date post: | 12-Nov-2014 |
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VirusesThe deadly microscopic world.
Viruses• Nucleic acid within a protein coat• Jenner – smallpox vaccine• Non-living• No metabolism• Cannot replicate without a host• No scientific name, instead family names
Influenza virus
Structure of a Virus
• Viruses that infect bacteria – bacteriophage
• General Characteristics:• Nucleic acid – either
RNA or DNA• Outer protein capsid• Optional features
for protection
• Envelope, spikes, slime layers
Capsid protein
DNA or RNATail
Tail fibers
Attaching to Cells • 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
Viral Replication Cycles
• Lytic 1A. Virus
attaches to cell
2A. Inserts DNA3A. Replication
of viral parts
4A. Assembly of new viruses
5A. Cell lyses
• Lysogenic1B. Virus attaches to
cell2B. Inserts DNA3B. DNA integrates into
host DNA - prophage4B. Cell replicates
normally with viral DNA altering protein synthesis
5B. Viral DNA comes out of the host DNA
6B. Begin Lytic Cycle
How Viruses Damage Cells• 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.
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
Viral Diseases
Smallpox•Last seen in 1977•Eradicated by WHO due to obvious symptoms and short life cycle•CDC and Moscow•Self-replicating
Chicken Pox•Fluid filled blisters•Itching and burning•Common in kids•Vaccine to prevent
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
Untreated shingles
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
Genital Herpes
Cold Sores •Herpes simplex•Virus lives in a nerve in face•Reactivated similar to shingles•Fever, sore throat, mouth pain, edema
Untreated cold sores
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•Symptoms treated with drug cocktail
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
Kaposi’s Sarcoma – HIV side affect
Burkitt’s Lymphom
a – HIV Side
Affect
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
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 nerves
Measles•Highly contagious•Respiratory droplet spread•Nasal discharge, dry cough, fever, headache, pink eye, pink lesions, ear infection•Targeted for eradication•MMR vaccine
Viral Hepatitis B• Initially asymptomatic•1-3 month incubation•Fever, loss of appetite, pain, nausea, fatigue, jaundice, swollen liver•3 step vaccine
Hanta Virus•Deermice and ticks•No human to human•2-3 day incubation•Cough, pulmonary edema, hemorrhaging, renal failure, achy muscles•60% death rate
Ebola•93% death rate•Hemorrhagic fever• High temperature• Blood from orifices
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
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
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
Viral Diseases• 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
A
B
J