Lecture 19-20 - Emerging Viruses Flashcards
What disease is probably the most communicable human disease known?
Measles or Rubeola
Does Rubeola have an iceberg effect?
No, almost 100% of non-immune individuals would quickly become infected and show disease
Measles is caused by what type of a virus?
Paramyxovirus
Measle Virus characteristics:
- Envelope or No envelope
- Genetic Material
- Transmission
- Can become immune?
- Enveloped
- (-)ssRNA
- Vertical transmission through Respiratory droplets
- Lifelong immunity to those infected
Where does the Measles virus attack first?
It initially replicates in the respiratory tract and the local lymphatic system. It then spreads via viremia throughout the body.
What causes the characteristic measles rash?
Tc cells targeting measles-infected endothelial cells of the capillaries
Explain the pathophysiology of the Measles virus
It causes cell fusion, leading to the formation of giant cells and allowing the viruses to pass directly from cell to cell and escape antibody neutralization. But Tc cells destroy viral factories resulting in elimination of infection.
How is the mortality rate of the Measles virus similar to influenza?
It is relatively low in both of these highly-contagious viruses
In those healthy individuals the die from Measles virus, what is usually the ultimate cause of death?
Viral-caused encephalitis
In poor populations: Usually because of viral and secondary bacterial pneumonia
Is mortality rate of Measles higher in poor and malnourished populations? Why?
Yes. The measles-induced immunosuppression synergizes with poverty-induced immunosuppression to cause excess mortality
Mumps virus Characteristics:
- Virus family?
- Envelope or No envelope
- Genetic Material
- Transmission
- Paramyxovirus
- Enveloped
- (-)ssRNA
- Respiratory droplets, Saliva, Contact (highly contagious)
Do Mumps have an iceberg effect?
Yes, a significant number of infected individuals do not show symptoms
What is the characteristic symptom of mumps
Parotitis - painful swelling of the salivary glands, especially the parotids
What is the Pathophysiology of Mumps
Viruses infect the salivary ducts and subsequent inflammation blocks the drainage of salivary fluids.,
Why might men not want to get Mumps????
Mumps may also infect almost any other gland of the body. This includes testicular ducts which occasionally causes sterility in adult males.. Not so good…
Rubella virus Characteristics:
- Virus Family
- Envelope or No envelope
- Genetic Material
- Transmission
- Togavirus
- Enveloped
- (+)ssRNA
= Spread by respiratory droplets
Rubella or German Measles is similar to Measles with this exception
It is comparatively benign and less infectious than Measles
What age group do we not want to contract this disease?
Unborn babies are at high risk of severe birth defects if their mothers contact the disease during the first trimester. If not for this, we wouldn’t worry much about Rubella.
What is the vaccine for Measles, mumps and rubella?
MMR vaccine. It is a live, attenuated combined vaccine. It is usually given between 12-14 months, with a booster just before school entry.
Which of the three diseases, Measles, Mumps, Rubella, affect only humans?
All of them are only found in humans.
Which is more dangerous out of Measles, Mumps and Rubella? Why?
Measles. It causes temporary immunosuppression that can synergize with poverty-induced generalized immunosuppression to allow opportunistic secondary infections
Measles causes small bluish white spots on the buccal mucosa called what?
Koplik spots
What is Zoonosis?
A disease that normally exists in other animals, but can be transmitted and also infect humans
3 Characteristics of an ‘Accidental Host’
- Not required for microbe’s existence
- Pathology can be severe
- May be dead-end host (microbe kills before transmission to the next host)
Explain the selective pressure on both microbe and accidental host during zoonotic infections
Microbes that rapidly kill a host will not generally be successfully transmitted- both host and microbe lose. Therefore there is a tendency over time to select for a middle ground, which may lead to an emerging disease.
- Microbe mutates and is selected for decreased pathogenicity
- Hosts are selected that are more resistant
Define Reservoir
hosts which serve to maintain and amplify pathogens in the enrivonments
3 causes of emerging viral diseases include:
- Mutation of human viruses - new virulence potential
- Mutation of animal or insect viruses - new ability to infect humans
- Recombination of viruses - yielding new human virulence potential
A virus with what type of genome is most likely to cause emerging viral diseases?
ssRNA viruses because their RNA-dependent, RNA polymerase is error prone, plus with no second strand, ‘proof-reading’ can’t happen.
Name 3 specific examples of ssRNA viruses that are recent examples of an emerging virus
HIV (ssRNA, retrovirus)
Influenza (ssRNA, Orthomyxovirus)
SARS (ssRNA, Coronavirus)
Define vector
an organism that transmits a pathogen from one organism to another.
What is the difference between an Accidental host and a Dead End host?
Accidental hosts are characterized by the agent being able to complete its lifecycle
Dead-End hosts are infected by agents but the agent is unable to complete its lifecycle or be passed to another person
Often times, pathogens cause very severe and even fatal illnesses in what kinds of hosts?
Accidental and Dead-End hosts. Because the pathogens and hosts aren’t adapted to one another.
What is Encephalitis
Acute inflammation of the brain
What is Hemorrhagic Fever
severe, multi-organ syndromes caused by vascular system damage (capillary blockage and bleeding)
What type of viruses contain a growing number of insect and rodent borne pathogens?
Several genera of Enveloped ssRNA viruses
Arboviruses and Roboviruses
Arboviruses and Roboviruses (Enveloped ssRNA viruses) often cause what two diseases?
Encephalitis and Hemorrhagic fever
Arboviruses has what 3 subcategories of viruses?
Togaviruses (+)ssRNA
Flaviviruses (+) ssRNA
Bunyaviruses (-)ssRNA
What is the subcategory of Roboviruses?
Arenavirus (-)ssRNA
Name a common example of a Robovirus?
Hanta Fever spread by rodents
Name a common Flavivirus (Arbovirus)
West Nile Fever
Name a common Filovirus?
Ebola
Prions cause what disease?
Transmissible Spongiform Encephalopathies
What is a Transmissible Spongiform Encephalopathy
a rare, slow, degenerative disease of the brain that result in a ‘spongy’ looking brain
Name the five disorders associated with transmissible spongiform encephalopathy
Humans:
1. Kuru
2. Creutzfeldt-Jakob Disease (CJD)
Animals:
3. Scrapie (Sheep)
4. Bovine Spongiform Encephalopathy (BSE, Cattle)
5. Chronic wasting disease (Deer and Elk)
What is a protein and how is it different than a virus
They are a modified host protein that can transmit disease
They have no virus structure or genome, elicit no immune response and are extremely resistant to inactivation by heat, disinfectants and radiation
What do prions consist of in their structure?
Aggregates of protease-resistant, hydrophobic glycoprotein generically termed PrP (prion protein)
How do prions cause disease?
- Protease-resistant PRP cause normal host PRP to fold differently, and become protease-resistant
- The increasing resistant PRP accumulate into abnormally large amounts called ameloids in the CNS.
- Accumulation of the resistant PrP deposits (Ameloids) causes fatal spongiform encephalopathy
Do Prions elicit an immune response?
No
How is Smallpox spread?
Through Respiratory droplets –> replicates in respiratory tract –> Macrophage Taxi –> Lymph Nodes –> Viremia
Know Edward Jenner STORY!!!! And that he may have not been the first to prevent smallpox or in other words, in the middle ages prevention was occuring.
Is this class over yet?
