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47 Cards in this Set

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What three Picornaviridae genera are pathogenic to humans?
1. Enterovirus
2. Rhinovirus
3. Hepatovirus
What is significant about the structure of a picornavirus?
1. VERY SMALL
2. positive ssRNA
3. icosahedron
4. non-envelope
5. space between VP1 and VP2:VP3 provide biding site for cellular receptor
6. host cell receptor that recognizes picornavirus is Polio Virus Receptor aka CD155
What does the structure of the picornavirus imply about the stability and route of transmission?
since there is no envelope, this virus is VERY stable in many different environments, which means that it can withstand the harsh conditions of the GI tract, which means it's transmission is fecal-oral
Are there animal reservoirs for enterovirus?
nope, which means that it can be eliminated by vaccine from human population
What is the pathogenesis of enterovirus?
1. pathogen is ingested
2. replication takes palce in oropharyngea
3. primary infection takes place in intestinal mucosa
4. systemic spread can occur from primary infection site
How long after exposure to enterovirus does a carrier being to shed and how long do they shed?
3-5 days after exposure
shed from throat for 1 week
shed from feces for several weeks
What is the classification of polio?
Picornaviridae Enterovirus poliovirus
What are the three infection outcomes based on the three serotypes of poliovirus?
1. asymptomatic - majority
2. systemic/symptomatic
3. paralytic
What age group is most concerning in regard to asymptomatic polio infection?
adults. as people age they are more likely to become symptomatically infected even if they have been asymptomatically infected in the past.
What is abortive polio?
a type of systemic/symptomatic infection of the poliovirus that causes about 5 days of malaise, prodrome but is self-limited
What is aseptic meningitis considered in a poliovirus infected individual?
this is the result of a systemic/symptomatically infected individual that has a secondary viremia that has spread into the meninges.
During what general time in history was systemic poliovirus infection most relevant?
pre-vaccination period of time.
What are the two types of paralytic poliovirus infection?
1. paralytic poliomyelitis - more common in the past -> paralysis due to spinal cord, brain stem infection
2. bulbar paralysis - cranial nerve nuclei or medullary center damage that caused cardiac, respiratory, swallowing problems that were often fatal
What is post-polio syndrome (PPS)?
spinal poliomyelitis that occurs decades after recovery from systemic or paralytic polio which causes a slow muscle weakness caused by anterior horn infection of the past
What happens to the neurons that are involved in PPS?
polio causes irreversible damage to motor neurons. when those neurons are gone, the neighboring neurons increase the number of motor units they control. as the pt ages, and those motor neurons begin to deteriorate, muscle weakness results more than in uninfected individuals. (pic)
Why is PPS dx annoying?
it is an exclusion diagnosis
What is PPS tx?
non-fatiguing exercise to increase strength of remaining muscle

no drug therapy has proven efficacious
Tx for polio?
supportive, but poliomyelitis is preventable to two different types of polio vaccines
What are the two types of polio vaccines?
OPV - oral live attenuated virus, not for immunosuppressed or pts over 18 y/o

IPV - injected inactivated polio virus that only vaccinates against systemic response because only provides IgG based prevention. prevents virus from getting to CNS
What is VAPP?
very rare circumstance that causes vaccine-induced paralytic disease
What is the IPV immunization schedule?
subcu or IM injections at the following intervals:
2 months
4 months
6-18 mos
4-6 years

there must be four doses and they must be at least 4 weeks apart, but the previous is the suggested schedule
What is the OPV immunization schedule?
not used in the US
Where is wild-type polio still found in the world?
Nigeria, India
What was the March of Dimes initially created for?
the fight to eradicate polio!
What are the three Enteroviruses that are relevant to this class?
1. poliovirus
2. coxsackievirus
3. echovirus
What are the two types of coxsackieviruses and how are they different?
Coxsackie A - herpangia, hand foot and mouth disease
Coxsackie B - infections of the "B"ody like myocarditis and pleurodynia
What is clinically significant about echovirus and coxsackievirus?
they are usually asymptomatic
What is herpangia?
disease a result of Coxsackie A where small, vesicular, ulcerated lesions occur on the soft palate of children. it is accompanied by flu-like symptoms and pain when swallowing, so kids don't want to eat. (pic)
What is hand-food and mouth disease?
Caused by Coxsackie A and B mainly in children and presents similarly to herpangia except not on the soft palate. more on the buccal mucosa, hard palate, gingivae, pharynx, lips, hands, heels. (pic)
How long does hand-food and mouth disease usually last?
typically 1 week
What causative agents of the picornavirus family are associated with aseptic meningitis?
Echoviruses and Coxsackie A and B specifically
What is pleurodynia/bomholm disease/devils grip?
Coxsackie B virus caused extreme and very quick onset of chest pain and prodrome feeling like the chest is tight and being gripped. last from 2 days to 2 weeks, usually self-limiting.
Pericarditis and myocarditis is caused by what echovirus?
Coxsackie B causes this in older children and adults which can present as prodrome and result in fatal heart failure
Neonatal myocarditis is caused by what echovirus?
Coxsackie B, same as pericarditis and myocarditis and is usually passed from mother during or shortly after birth.
What is the pathogenesis of Coxsackie B that causes myocarditis?
1. Coxsackie B infects cardiomyocytes and macrophages and replicates
2. destruction of initially infected cells occurs by lysis
3. viral proteases like viral protease 2A cleave host proteins like dystrophin and cause fibrosis and impaired contractility
4. immune response ensues
5. exudate and immune response goes auto-immune to continue to destroy heart cells
What is the tx for Coxsackie infection?
supportive, limit activity, limit salt intake, analgesics to limit inflammation
Where in the respiratory track to Rhinoviruses act and cause the common cold?
UPPER RESPIRATORY TRACT because they prefer to replicate at 33 degrees
Why can the Rhinovirus common cold not be easily stopped?
there are more than 115 serotypes and that number increases
What is structurally different between Rhinoviruses and Enteroviruses?
Rhino sticks to the rhino and can't move to the entero because rhino are acid labile!
How are Rhinovirus and Eternovirus similar?
icasohedron shape, non-enveloped
How are Rhinovirus spread?
respiratory droplets, contact with fomites with as little as a single virion
What is the Rhinovirus pathogenesis?
1. rhinovirus attaches to ciliated epithelial cells per virus attachment proteins and ICAM-1 receptor on the host
2. virus enters cell and infects causing cell to release bradykinin and histamine and at this time there is maximal virus shedding
3. virus replicates in cell (mostly in nose)
4. virus spreads to neighboring cells
Why is the release of IFN problematic with rhinovirus infection?
IFN is meant to produce an anti-viral state in a virus probable environment. as a part of that mechanism, it cause up-regulation of ICAM-1 on the cells' surface. ICAM-1 is used by rhinovirus as the receptor on the host. oops.
Why is immunity to rhinovirus and the common cold probably not gonna happen?
there are too many serotypes. we have somewhat transient immunity that is serotype specific.
What is the average rhinovirus incubation period?
2-3 days normally. up to 7 days.
What kind of mucus discharge with rhinovirus infection?
watery, clear discharge
What is the Tx for rhinovirus infection?
supportive. vaccines are ineffective because of the variable serotype.