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54 Cards in this Set
- Front
- Back
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Whats rhinitis?
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– inflammation of internal area of nose caused by Rhinoviruses and coronaviruses
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Rhinoviruses differs from other enteroviruses in that
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Replication limited to the respiratory tract
Due to acid liability (pH=6 inactivates) Optimal replication at 33 C |
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Rhinovirus pathogenesis
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1) Only human reservoir
2)Binds ICAM 1 on upper resp tract epithelial cells 3) extends locally w/o killing cells 4) Local inflammation causes exudate 5) Further ICAM 1 proliferation leads to more viral binding and infection 6) exudate may block passageways 7) Secondary sinusitis or otitis media |
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Why do we get repeated colds?
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-Viral receptor is in a depression (canyon) around the vertices of each pentamer.
-Antigenic determinants of each serotype are located primarily along the canyon rim on the surface of the virus particle. -Less critical surface residues around the canyon “drift”, giving rise to over 100 serotypes of rhinovirus |
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Whats the most commonly known effect of rhinovirus?
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common cold 50% due to rhinovirus
Coronavirus 30% |
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Rhinovirus transmission
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-Direct contact with contaminated hands & surfaces (fomites)
Most efficient -Inhalation of infectious droplets |
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Who is at risk of rhinovirus?
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Everyone
Rate of clinical symptoms decrease with age Attributed to partial immunity from past exposures |
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Rhinovirus most commonly in
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Early fall-late spring
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Influenza more common in
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Winter-Jan-Mar
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Patient presents with runny nose, sneezing and irritable throat and a slight fever. She suffers similar symptoms every year often at the same time as other members of her family. Her symptoms go away within a week, except for the nasal discharge that persists for a few months
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Rhinovirus
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Rhinovirus diagnosis
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Typically made based on clinical criteria
Symptoms of several common cold viruses are indistinguishable Usually do not test to identify specific “common cold” virus |
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Complaining of feeling tired and achy for few days
Today: Congested, thick yellow nasal discharge Non-productive cough started this morning No fever |
the common cold
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whats the relation between common cold and Acute Bacterial Sinusitis
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Acute bacterial sinusitis is a complication of colds. And it is a small percentage of the cases.
Nasal congestion/ purulent nasal discharge WITH facial pain Persistent; no improvement >10-14 days or worsening after 5 day |
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Common cold tx
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hydration and rest
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Coronaviridea Characterization
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Positive sense ss RNA genome (27-30kb)
LARGE (27-30kb) (largest RNA virus) RNA is capped and polyadenylated like mRNA Enveloped Irregular shaped particles (100-160nM) |
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Except for SARS coronaviruses infection limited to
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limited upper respiratory tract
Due to Optimal replication at 330 |
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Severe acute respiratory syndrome
coronavirus |
SARS-CoV)
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Coronavirus Features
Envelope glycoproteins |
S - Spike (formerly E2)
Receptor binding Cell fusion E - Envelope (formerly sM) Small, envelope protein (not as abundant as S) M - Membrane protein (formerly E1) Transmembrane Budding & envelope formation |
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Coronavirus Replication
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ENTRY:
Spike (E2) glycoprotein binds cell virus fuses & releases RNA into cytoplasm PROTEIN SYNTHESIS PHASE I: Translation of RNA-dependent Polymerase REPLICATION: Negative Strand Synthesis (RdRp uses viral genome as template for minus strand RNA synthesis) Positive Strand Synthesis (RdRp uses negative strand as template for genomic RNA AND a nest set of 3’ co-terminal mRNAs) PROTEIN SYNTHESIS PHASE II: All other viral proteins are translated ASSEMBLY AND SECRETION: Genome associates with Nucleocapsid proteins, which buds into ER for exocytosis |
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Coronaviruses infection can be asymptomatic but can cause enteric infections in
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infants younger than 1 yr
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Cornavirus Transmission:
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Direct contact with contaminated hands and surfaces
Inhalation of infectious droplets |
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Who is at risk for coronavirus infections?
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Everyone, but rate higher in children
(Re-infection can occur even in presence of serum antibodies) |
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When is coronarivures most common
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Dec-May
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SARS Unique Pathogenesis
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Causes upper and serious LOWER respiratory illness
Asymptomatic or mild illness uncommon |
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SARS Transmission:
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Patient-to-patient variability in transmission efficiency
Seems to correlate with illness & viral titers (Reservoir believed to be wild horseshoe bats) |
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Who is at risk of getting sara?
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Everyone, BUT
Age is important risk factor for severe disease Children have less severe illness than adults Fatality in the elderly can approach 50% |
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Why might age-based response be different than common cold
were children have worse illness? |
Age based response is different because the damage is due to immune system mediation. Older people have co-morbidities that worsen the condition.
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Coronavirus replicates best at
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33 - 35 0C and is therefore usually restricted to upper respiratory tract
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Whats the clinical SARS manifestation?
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Phase I – Systemic illness (fever, myalgia, chills, headache)
Phase II – Respiratory illness (cough, SOB, O2 desaturation) & diarrhea 3) Recovery or progressive respiratory failure |
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SARS Case Suspicion
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High fever (>380C) with
Cough or breathing difficulty and: -close contact with a probable case of SARS -history of travel to an affected area -residing in an affected area SARS Case Probable The above with evidence of change on chest X-ray |
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SARS reservoir is
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wood bat
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The single most important cause of
severe diarrheal illness in infants and young children in both developing and developed countries worldwide |
Reovirus
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Whats the only virus that is dsRNA and affects humans?
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Reoviridae Rotavirus
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Reoviridae Rotavirus structure
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Non-enveloped, icosahedral particle
- tough two-layered structure - can survive in the environment |
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Reoviridae Rotavirus tropism is for
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Differentiated Enterocyte
(small intestine) |
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How does Rotavirus infect?
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an intermediate/infectious subviral particle (ISVP)
The ISVP binds, penetrates the cell, and loses its outer capsid Inner capsid enters host cytoplasm (which contains the viral polymerase |
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Whats the ISVP?
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It is the rotavirus with the minor outer membrane capsid (major (VP7) is digested by GI tract proteases)
Attachment Protein VP4 is exposed |
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Whats the core of the rotavirus composed of?
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Inner capsid contains the enzymes for RNA synthesis
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Rotavirus replication
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viral mRNAs synthesized from negative-strand of genome
-viral mRNAs released into cytoplasm Host cell ribosomes translate viral proteins Viral proteins and positive-sense RNA associate into core structures Viral negative strand RNA synthesized in the core (to re-create dsRNA genome Core Structures aggregate into large cytoplasmic inclusions Virus Assembly and Release: |
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Orthoreovirus
transmission |
- respiratory & fecal-oral
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Ortheovirus affects
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individuals are infected in childhood
-75% to 80% of adults have antibodies |
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Ortheovirus detected by
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by RNA
-throat, nasopharyngeal, and stool specimens -No specific diagnostic tests recommended No specific treatment recommended |
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One of the most common tick-borne diseases in US
Virus infects erythroid precursor cells resulting viremia that may last for weeks & aids in transmission of virus to tick |
Coltivirus and Orbivirus
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Coltivirus most common in
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March to September (Spring to Fall)
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Coltivirus colorado tick fever manifestation
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Biphasic disease :
Fever, chills, headaches, pain behind the eyes, light sensitivity, severe myalgia & lethargy, abdominal pain, nausea, rash Rare Outcomes include: Neuronal infection causing aseptic meningitis, encephalitis Hemorrhagic disease from infection of vascular endothelial Diagnosis: - Patient’s recent activities/location or presence of TICK Treatment: – No specific treatment other than remove tick |
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the primary cause of infantile diarrheal disease
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rotavirus Group A: G1 (VP7 serotype) accounts for 73% of infections
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Who is at Risk? of rotavirus type A
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Infants at risk for infantile gastroenteritis
Older children and adults at risk for mild diarrhea |
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Who is at Risk?
Rotavirus Type B |
Everyone at risk for severe gastroenteritis
Mainly found thus far in China |
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Rotavirus most common in
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common in fall and winter
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Rotavirus Clinical Manifestations
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Disease:
Asymptomatic or Severe First infection generally being the most severe Symptoms Dehydrating diarrhea with fever and vomiting Electrolyte imbalance Generally resolves in 3 to 7 days |
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Rotavirus Disease Mechanisms
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Typical viral pathology
Cytolytic release of virus First viral enterotoxin Toxin-like action of viral protein NSP4 on the intestinal epithelium Increases intracellular Ca++ Effects PM permeability Resulting in loss of electrolytes & impairs water absorption. MECHANISM SIMILAR TO BACTERIA |
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Rotavirus Treatment
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Supportive Therapy:
Replace fluids so that blood volume, electrolyte and acid-base imbalances are corrected Oral Rehydration Salts (ORS) Solutions Intravenous fluid administration |
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Rotavirus Prevention
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Natural infection does not provide complete
protection against subsequent infection Very unlikely we can develop a vaccine more effective than the virus itself Result: The aim of any Rotavirus vaccine is not necessarily to prevent infection, but prevent severe gastroenteritis |
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Rotavirus Two Vaccines
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Rotavirus Vaccine (RotaTeq®)
Approved by FDA in February 2006 5 re-assortant rotaviruses from human & bovine strains Received ACIP* recommendation for routine vaccination Rotarix® Rotavirus Vaccine Approved by FDA in April 2008 1 strain of live attenuated human rotavirus (G1P1A) |
