Lecture 19-20: Viruses- New and Old Flashcards
Does the Measles cause an iceberg effect explain?
No iceberg effect, is the MOST communicable human disease known.
What is Measles (Rubeola) ?
Paramyxovirus (-) ssRNA, Eveloped.
How is Measles transmitted?
- Through respiratory droplets via viremia throughout body.
- Highly contagious
- virus replicates in the lymphatic system and respiratory system
What causes the characteristics measles rash ?
Cytotoxic T cells killing viral infected endothelial cells
causes results in characteristic rsh and koplik spots in oral cavity
How is the infection of measles eliminated?
Tc cells destroy all of the viral factories and Abs stop the formation of new factory, together resulting in the complete elimination of the infection.
What is the greatest cause of increase morbidity and mortality with Measles?
Malnourishment and compromised immune system.
***Because it causes temporary immunosuppression that can synergies with poverty-induced generalized immunosuppression to ALLOW OPPORTUNISTIC SECONDARY INFECTIONS!
Why are poorer developing countries more likely infected with Measles?
Measles causes a temporary generalized immune suppression. This the measles induced immunosuppression synergies with poverty induced immunosuppression to causes excess mortality.
What are the characteristics of Mumps?
Caused by an enveloped (-) ssRNA Paramyxovirus (just like Measles).
-Unlike measles there is an ICEBERG EFFECT (significant number of infected individuals who do not show symptoms :( and fewer deaths.
What are the symptoms of mumps?
- ***Parotitis (painful swelling of the salivary glands, especially the parotid)
- Viruses infect the salivary duct and subsequent inflammation blocks the drainage of salivary fluids.
- Will also affect testicular ducts (causing sterility)
What is Rubella (German measles)?
Similar disease to measles, but is less benign and less infectious.
-Unborn babies are at high risk of severe brith defects (25% of the time) if mothers get the disease during the 3rd trimester.
-Without neutralizing Abs the virus can pass across the placenta and infect the developing fetus –> severe consequences
What are the characteristics of Rubella virus?
- enveloped + ssRNA Togavirus
- Also spread by respiratory droplets like the previous two.
What is the MMR vaccine?
Measles, Mumps, and Rubella can be prevented by a live attenuated, combined vaccine.
-Given btwn 12-14 months and boosters thereafter.
What do all three of these viruses have in common?
- They are only found in humans
- mostly common to children
- Enveloped viruses ss RNA
Out of the three diseases which one is most important and still causes deaths annually?
Measles!
- 200,000 deaths still occur in small children.
- WHO set a goal to eradicate measles by 2010.
- Vaccination rates have declined due to a fraudulent report linking MMR vaccine w/ autism (false btw).
What does the Viremia of measles lead to ?
1) Encephalitis and 2)immune suppression–>Viral pneumonia–>secondary opportunistic infections.
3) Endothelial epithelial–>koplik spots (bluish-white buccal mucosa) + rash
What happens when mother in her first trimester is infected with Rubella.
The fetus has a significant chance of developing severe deformities
Why is the vaccination for Rubella unique compared to other vaccines?
All the benefit goes to those yet to be born helping the next generation.
What is the pathology of congenital Rubella?
Rubella–>resp droplets–> resp. tract–>lymphoid replication–>Virema–>Mom–>placenta, lungs, skin,joints–> congenital rubella
What is zoonosis?
A disease that normally exists in other animals but can be transmitted and also infect humans
What are accidental host?
Not required for microbes existence
- pathology can be severe
- may be dead-end-host (microbe kills before transmission to the next host)
What is reservoir?
A normal host required for a microbes existence which **serves to maintain and amplify pathogens in the environment.
What gave rise to many serious disease of humans (HIV and measles?)
- Mutations in both the microbe and accidental human hosts, and subsequent selective pressures probably gave rise to this.
- Increasing human populations and quicker transportation times
Hunter/Gathers (small, isolated groups ) affects zoonosis ?
infrequent –>quickly “burns out”
where as herders/farmers = more frequent –>plagues and emerging disease
***Why are enveloped viruses over expressed/emerging diseases?
Because of their fragile nature need to have direct contact with people and there are so many creatures that humans have not had encountered. Hard to make the leap to us.
Infection like _____ where you live of die, it is an acute illness and no carriers.
Measles burns out quickly after infections all.
With _________ you are infected 90% and only 10% chronically infected for life. (carriers)
HBV
*Emerge all the time and does not burn out.
What are emerging viral diseases?
- Known diseases increasing in incidence or geographic range
- New infectious agents causing new (or previously unrecognized) diseases.
What are the causes of emerging viral diseases ?
1) Mutation of human viruses –> new virulence potential
2) Mutation of animal/insect viruses–> new ability to infect humans
3) Recombination of viruses –> yielding new human virulence factor
Why are ssRNA viruses more likely to cause the emerging viral diseases?
they are RNA dependent, RNA polymerase is error prone (no spellcheck), plus no second strand , proof-reading cant happen.
What is the primary example of an emerging ssRNA retrovirus ?
HIV
What are two other examples of an emerging ssRNA viruses?
Influenza (orthomyxovirus) (-) ssRNA (H1N1-swine)
SARS (coronavirus) ssRNA (viral pneumonia)
What are vector borne viruses?
-Emerging diseases carried by insect or animal vector.
An organism that transmits a pathogen from one organism to another.
What are Dead-End Hosts?
Those in which the infectious agents do not normally develop but when occasionally change infection do occur, the agent is unable to complete its lifecycle, produce many infectious particles, or be passed onto another person.
***Infection reaches a dead end.
Why do the pathogens often cause very severe even fatal illnesses in these hosts?
Since the pathogens don’t need the accidental or dead-end hosts for their continued existence, and the pathogens and the accidental and dead-end hosts have not “adapted” to one another, the pathogens often cause very severe even fatal illnesses in these hosts.
Which enveloped ssRNA viruses contain a growing number of these insect and rodent borne pathogens ?
Arboviruses and roboviruses respectively
Arboviruses and roboviruses can cause what?
Encephalitis and Hemorrhagic fever
What is encephalitis?
acute inflammation of the brain
What are Hemorrhagic fevers?
Severe, multi-organ syndrome cause by vascular system damage (capillary blockage and bleeding)
**No cure
What is the exception to the Togavrius group that spreads usually by arthropods?
Rubella is the exception because it does not spread via arthropod it spread via respiratory droplets!
Other like West Nile, Dengue, yellow fever use arthropod vector.
Ebola what kind of vector-borne virus?
Filovirus that is (-)ss RNA
-enveloped, zoonotic virus
Hanta fever is what kind of vector-born virus?
A Robovirus that is (-) ssRNA
-enveloped, zoonotic virus
Dengue fever, and West Nile fever is spread by what vector-born virus?
Arbovirus that belongs to the subgroup, Flavivirus that is (+) ssRNA
-enveloped, zoonotic virus
Rubella is spread by what vector borne eveloped virus?
(+) ssRNA Togavirus that belongs to the Arboviruses (arthropod borne)
This can lead to encephalitis
-enveloped, zoonotic virus
What are the effects enveloped RNA viruses have on these organs, lung, brain, liver, and endothelium?
Pneumonia, encephalitis, hepatitis, and hemorrhagic fever.
*serious outcomes.
How do Arboviruses differ from roboviruses?
Arboviruses transmitted via bite and roboviruses have fecal transmission.
Why are ssRNA viruses (HIV & Ebola) more likely to make a jump to a new species ?
Because of the often high mutation rate found in ssRNA viruses.
- Generally zoonotic pathogens reside in animal/insect reservoirs and are dependent on these hosts.
- When these viruses are “accidental” pathogens to humans it can spread quickly among the local human population causing significant morbidly & mortality.
What are prions ?
-Modified host proteins, which can transmit the disease
- Cause transmissible spongiform encephalopathies.
- They are rare slow, degenerative diseases of the brain that result in a “spongy” looking brain. (Holes where neurons should be)
What disease can prions cause?
1) Human disease Kuru and Creutzfeldt-Jakob Disease (CJD)
2) Animal diseases Scrapie (sheep) , Bovine Spongiform Encephalopathy (BSE) cattle*, and chronic wasting disease (deer and elk)
How do prions differ from viruses?
These agents have no virus structure or genome, elicit no immune response, and are extremely resistant to inactivation by heat, disinfectant, and radiation.
What are the components of infectious prions?
lack detectable nucleic acids, consists of aggregates of protease-resistant, hydrophobic glycoproteins generically termed PrP (prion protein)
How do prions cause disease?
- Protease-resistant PrP (PrPres) cause normal host PrPsen (which is protease sensitive) to fold indifferently, and become protease-resistant like the original PrPres.
- The increasing amount of PrPres proteins accumulate into abnormally large amounts (called amyloid ) in the CNS.
- This accumulation of amyloid deposits (or/and lack of function of normal PrP) causes fatal spongiform encephalopathy.
Why does our immune system not generate an immune response to prions?
Because the body does not see the prions (proteins) as foreign.
How are the normal proteins folded into an abnormally stable form?
-These mis-folded proteins cause normal proteins to mis-form when they come together.
-Stable form acts to mold many copies of host proteins into abnormally stable form.
(PrPres+ PrPsen –> 2 PrPres)
What is the result of PrP misfolding?
Amyeloid buildup–>brain damage–> disease
What is Scrapie?
- Caused by protease -resistant prion protein (which should help normal proteins turn-over) when this goes wrong and protein are not degraded and they are mis-folded and causes other proteins to misfold.
- Old disease that causes sheep to scrap off their skin at those sites and they die. They found that agent that caused it was resistant to heat, u.v, protease/nucleases, and formaldehyde.
What is the agent of Prion disease?
Protease-resistant-prion-protein (PrPres)
How was human transmissible spongiform encephalitis caused?
In New Guinea there was a ritual brain consumption and this caused a slow accumulation of this disease. This was because these brain tissues had prions.
What is CDJ disease?
a rare spontaneous transmittable prion disease.
1 and a million people infected.
-Every creature that has a brain can have a weird event that occurs with their prion proteins mis-folding.
What is BSE (Bovine spongiform encephalopathy) (*MAD COW DIS)
- offal in brain (crap on the floor) used to “bind hamburger”
- **(similar in cats too)
- They mixed it with grain and fed it back to the cows
- A cow got infected slowly the cow population
- transmitted cow to cow
- Seen in the USA in 2003
What is smallpox?
- Very LARGE dsDNA virus.
- Poxvirus, caused by Variola virus
- Category A
- We think the disease jumped from cows
How is small pox spread?
- Spread via respiratory droplets, very contagious.
- Replicates in the respiratory tract
- Uses the Macrophage taxis and ends up in the blood stream, kills off the internal organs–>lymph nodes
With small pox what does Viremia cause ?
1) organs: spleen, liver, etc to shut down
2) skin of survivors scarring and blindness.
How many people did small pox kill?
Killed 1/3 of the population and left another 1/3 with terrible scars.
-Now smallpox is the only human disease eliminated from the world!!!!!!!!!
What is variolation?
Collecting scabs and putting them in a jar, turning them to powder scabs. Then putting then in the skin by breaking the skin and making one immune.
Who was Lady Mary Wortely Montagu and Edward Jenner?
Lady Mary used variolation and introduced it to England.
Edward Jenner hypothesized that cowpox gave immunity to smallpox so injected a boy and he was immune.
-That is how vaccinations were born! (Vacca=cow)
