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Block 3 MICRO Exam -- Emerging Negative Strand RNA Viruses (#8)


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Classic progression of an emerging virus
Original host lives in forest
Deforestation results in grain crops
Rodent is introduced, becomes infected
Virus introduced through man via rodent
Three genera within paramyxomviridae
Pneumovirus (RSV)
Common route of transmission for all paramyxoviruses
Respiratory droplets

Note: RSV can also spread via contaminated hands
Three proteins that protrude from paramyxovirus envelope
F (fusion) protein
Interesting mRNA charac. of paramyxoviruses
Contain internal "start" and "stop" sites

NOTE: each mRNA encodes a single protein
Where does initial replication of measles take place?
Respiratory epithelium
How long is the incubation period of measles?
5-10 days
When does measles pt. lose infectivity?
Right after the rash appears
Pattern of progression of measles rash
Begins at the head
Moves down to the extremities
As it moves down, disappears from upper parts
Koplik spots
Characteristic oral lesion of measles
Potential sequelae of measles
Otitis Media

Autoimmune Post-infectious myeloencephalitis
Measles inclusion body encephalitis
Giant cell encephalitis
Sub-sclerosising pan encephalitis
Autoimmune Post-infectious Encephalomyelitis
Immune sequelae to measles
Cross-reactive repsonse to MYELIN BASIC PROTEIN
Sub-sclerosing Pan Encephalitis
Sequelae of measles (RARE)
Progressive neurologic disease of children

Can cause deterioration, seizures, motor abnormalities

Frequency of 6-22 cases per million
Viruses responsible for Croup
Parinfluenza, RSV, Influenza
Type of vaccine for MMR
Live attenuated
Characteristic glands swollen in mumps
Salivary glands
Inflammation of testis
Secondary to MUMPS

NOTE: can be sterilizing
Secondary infections to mumps
Meningitis/Encephalitis (10%)
Which is more likely to cause some form of encephalitis?

Mumps or Measles
Mumps (10%)

The encephalitides of measles are very rare
Problem w/ "disastrous" RSV vaccine
Over-response of TH2 cells
NOT down-regulated
How many segments in Bunyaviridae genome?
THREE segments
Main disease(s) caused by Bunyaviruses

Can progress to seizure/coma
BUT, majority are subclinical
Main disease(s) caused by Phleboviruses
Fever (Sandfly, Rift Valley)

NOTE: In RF fever, encephalitis or hemorrhage can occur
Main route of transmission of hantaviruses to humans
Aerosolized excreta
Main disease(s) caused by Hantavirus
Hemorrhagic Fever with Renal Syndrome
Sin Nombre
Main route of transmission of Phleboviruses
Sin Nombre
Hantavirus PULMONARY syndrome

Mild onset, flu-like symptoms
Rapidly progresses to kidney failure w/ internal bleeding


Mortality is 40 - 60% (varies w/ strain)
Vector for Hantaviruses
Rodents and birds
Hantavirus-induced hemorrhagic fever w/ renal syndrome leads to what?
Interstitial nephritis

Mortality rate 5 - 35%
Main disease(s) caused by Nairoviruses
Crimean-Congo Hemorrhagic Fever
Crimean-Congo Hemorrhagic Fever
Caused by Nairovirus
Primarily zoonosis, infrequent in humans

Length of incubation depends on vector (blood > tick)

Abrupt fever, neck pain, sore eyes, photophobia
May experience sharp mood swings
Ab pain in RUQ, noticeable hepatomegaly
Causes "sandy" appearance of arenaviruses
Numerous ribosomes
Special characteristics of Arenavirus RNA
Segmented (2)
Ambisense orientation
Ambisense replication
Each strand encodes opposite reading frames
Thus, each fram is used for different proteins
Vector for Arenavirus
Virus family for Lassa virus
How are arenaviruses shed?
In urine
Lassa Fever
Muscle aches, mild fever, N&V
SEVERELY bloodshot eyes, Painful rash (subdural hemorrhage)

All tissue become inflamed and begin to bleed

Mortality is 70%
Most dangerous viral families
Virus family for Ebola virus
Filovirus replication is most similar to what type of virus?

("start" and "stop" sequences)
Filoviruses bud through what?
Host cell membrane
Nascent filoviruses contain what special types of proteins?
(Hint: contribute to hemorrhage)
Protein that mimic those in coagulation pathway

Cause clotting factors to become depleted
How do filoviruses spread within an organism?
What is the usual cause of death from Filoviruses?
Heart failure

Mortality rate of 50 - 90%
How are filoviruses transmitted?
Blood-borne transmission
Incubation period for filoviruses
2 - 21 days
Disease caused by filoviruses

All tissues become inflamed and bleed
10 days after symptoms, pt. vomits and defecates blood

Mortality of 25%
Protein responsible for Ebola's cytotoxic effects
Relative incubation periods for Ebola
Needle-stick -- 5-7 days
Person-person -- 6-12 days
Virus family responsible for Ebola virus
Diseases caused by prions
Chronic Wasting Disease
Bovine Spongiform Encephalopathy
Creutzfeldt-Jakob Disease
Fatal Familial Insomnia
Featurs that distinguish prions from viruses
Multiple molecular forms
NON-immunogenic (considered "self")
NO essential nucleic acid
Only known component of prions
Function unknown
How is mutation rate rleated to genome size?
Inverse correlation
For the same size, which has higher mutation rate?


Lack error-correcting mechanisms
This virus has a "hubbed wheel" appearance on EM
Leading cause of viral gastroenteritis

95% of all children infected by age 5
Peak incidence of rotavirus diarrhea
Between 6 and 24 months of age
How is rotavirus transmitted?
Fecal-oral route
When is peak transmission rate of Rotavirus?
3rd day of illness

Transmission can continue for two weeks after symptoms abate
Majority of rotavirus pts. have this in their stool

May be heme+ as well
What cells does Rotavirus infect?
Mature enterocytes in MID & UPPER part of villous
How does Rotavirus enter cells?
Calcium-dependent endocytosis
Mechanisms behind Rotavirus action
Loss of absorptive area
Inhibition of sodium-coupled transport
Increased paracellular permeability
May activate enteric nervous system
What is charactertistic about the stool in Rotavirus?
Usually contains fat
Often excessive acid content

Acidity due to fermentation of undigested CHO
Treatment options for rotavirus diarrhea include
Anti-diarrheals (Loperamide, Acetorphan)
Oral Immunoglobulin

Nearly half of the deaths from Rotavirus are due to what?
Breast feeding effect on Rotavirus protection
During first yr. of life, LOWERS risk

During second yr. of life, RAISES risk
Significant medical problem that came up in Rotavirus vaccine research?

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