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49 Cards in this Set

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  • Back
3 main genera within picornaviruses that infect humans
Enteroviruses
Heparnaviruses
Rhinoviruses
Poliovirus is part of what genera
Enterovirus
Where do they enteroviruses replicate
GI tract
Transmitted by fecal-oral route

NOTE: do NOT cause severe GI disease
Where do rhinoviruses replicate
Nose & upper respiratory tract
What is the site of recognition of picornaviruses for virus receptors?
Cleft in VP1 protein
These picornaviruses are NOT sensitive to acid pH
Enteroviruses

Includes: poliovirus, coxsackie, echo, entero
Capsid proteins are at what end of the picorna RNA
5' end
IRES
Internal Ribosome Entry Site

Serves same purpose as RNA cap, which these do NOT have
VPg
Primer in RNA replication at 5' end
Removed to allow translation to begin
Where does picornavirus replication take place?
ENTIRELY in cytoplasm
This event transforms procapsid into a mature capsid
Proteolytic cut in one of the casid proteins
How long does picornavirus replication cycle take?
6 - 8 hours
How do picornaviruses overhaul cellular machinery?
Cleave and inactivate host protein that recognizes mRNA "cap"

Stops host cell synthesis
BUT, viral synthesis can continue due to IRES
What type of paralysis does polio cause?
Flaccid

From destruction of motor neurons
Which polio serotype causes most paralysis?
Serotype 1
How does poliovirus spread in the body?
Hematogenously
How long is the incubation period of poliovirus?
7 - 14 days
Abortive polio
~90% of cases or more

Sore throat or GI symptoms
NO neurological problems

Resolves in a few days
Non-paralytic polio
5% of cases

Back/Neck pain, muscle spasms
Spreads to CNS, but NO paralysis

Recovery is complete after 2-10 days
Paralytic Poliomyelitis
~1% of cases

ASYMMETRIC, FLACCID paralysis
May be accompanied by meningitis
NO SENSORY LOSS

Maximal recovery ~6 months
Recovery is almost NEVER COMPLETE

Recovery results in lifelong immunity
Post-polio syndrome
Muscle wasting and mild paralysis

Can occure 30 - 40 yrs after primary disease

NOTE: NO viral growth during this
Binding of what can neutralize poliovirus?
Neutralizing epitopes on VP1
How long does passive immunity (mom-->kid) last against polio?
~6 months
What types of vaccines are available for polio?
Killed (Salk)
Live attenuated (Sabin)
Reservoirs for polio
HUMAN ONLY

BUT, can be transferred to monkeys
Seasonality of polio
Temperate climate -- summer/early fall

Tropics -- all year long
Age group most at risk for polio
5 - 15 yr. olds
Type A coxsackie only are most usually found in what diseases?
Herpangina
Hand-foot-mouth
Acute hemorrhagic conjuctivitis

Think face/mouth
Type B coxsackie only are most usually found in what diseases?
Pleurodynia
Myocarditis
Meningoencephalitis

Think heart/chest/brain
When are coxsackie virus infections most common?
Summer
How do coxsackie viruses spread within body?
Hematogenously
How long is the incubation period for coxsackie viruses?
2 - 9 days
Herpangina
Severe febrile pharyngitis
Onset is abrupt
Only a few days duration (self-limiting)

Caused by some GROUP A coxsackie viruses
Pharynx has characteristic vesicles on palate

Can affect any age group, but children @ highest risk
How is Hand-Foot-Mouth disease distinguished from Herpangina
HFM lesions occur more towards ANTERIOR mouth
Palms and soles are involved in HFM
HOw is HFM distinguished from chicken pox
HFM almost always involves the mouth
Chicken pox makes people more sick
Hand-Foot-Mouth Disease (HFM)
Ulcers in mouth, and vesicular rash on palms/soles
Rash may spread to arms/legs

Most common in children

Caused by Group A Coxsackie viruses
Pleurodynia
Also called Bornholm's disease

Sudden onset fever and chest & ab pain
Pain worsened by movement and breathing

Caused by Group B Coxsackie

Most common in children
Lasts week or so
Relapses may occur
Coxsackie-related myocarditis is worst in what age group?
Newborns
What viruses cause Acute hemorrhagic conjuctivitis
Enterovirus 70
Coxsackie virus A24
What is incubation period in case of acute hemorrhagic conjuctivitis?
Very short - 24 hrs.
Cases resolve spontaneously in 1-2 weeks
What other infections can coxsackie viruses cause?
Coxsacikie A alone -- diarrhea
Coxsackie A & B -- common cold
Seasonality of common cold
Early Fall
Late Spring
Non-rhinoviruses that cause common cold
Parainfluenze
Adenoviruses
Coronaviruses
Enteroviruses
What other animals canbe infected with rhinovirus?
Gibbons
Chimps
Conditions that rhinoviruses survive or succumb to
Inactivated @ acid pH (3)
Replicate best @ 33 degrees C
Very stable to dehyrdation
Most important methods of rhinovirus transmission
Self inoculation (fingers, etc.)
Aerosol
How long does it take for Ab to show for rhinovirus?
7 - 21 days

NOTE: this is after disease has cleared (takes 3-7 days)

Ab is protective against subsequent infection of SAME serotype
Why is rhinovirus vaccine unlikely?
Poor growth in cell culture
TOO MANY serotypes
Which picornavirus does NOT grow well in cell culture?
Rhinovirus