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35 Cards in this Set
- Front
- Back
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What are the notable Paramyxoviruses? |
This chapter: parainfluenza, Respiratory syncitial virus, human Metapneumovirus
mumps and measles |
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Paramyxovirus virus (parainfluenza, RSV, hMNV):
basic structure of the virion? enveloped? does the nucleocapsid contain the viral polymerase? |
Helical single stranded negative-sense RNA enveloped nucleocapsid contains viral RNA transcriptase |
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Paramyxovirus virus:
steps of the viral replication cycle? site of replication and assembly? how are virions released? |
1. Entry via receptor binding, fusion. a. viral mRNAs |
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Paramyxovirus virus replication:
1. Entry via ? |
1. Entry via receptor binding, fusion. a. viral mRNAs |
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What additional proteins does RSV have that may be immune system targets? Which one has the highest variability among strains? |
F = fusion G = attachment = highest variability |
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Parainfluenza virus:
transmission? populations at highest risk? |
Transmission is mostly by contact, fomite or large droplet
< 1y/o at risk for more severe disease |
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Major disease presentations of parainfluenza virus? |
URT = mild disease/cold
LRT = croup, bronchiolitis |
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Where is the obstruction when you hear:
Inspiratory stridor Expiratory stridor Biphasic stridor |
Inspiratory stridor = obstruction above the glottis Expiratory stridor = intrathoracic obstruction Biphasic stridor = either critical obstruction or an obstruction in the area between the glottis and subglottis. |
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When do types 1 & 2 parainfluenza have outbreaks? type 3? |
Types 1&2 outbreaks in fall and winter
Type 3 is endemic and primary infection occurs early in life |
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What lab tests are used to diagnose parainfluenza virus? |
direct fluorescent antibody test
Rapid identification by direct fluorescent antibody test can distinguish 1, 2, and 3 and has been generally what is relied upon clinically. |
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What type of cells does parainfluenza infect? Mechanism of pathogenesis of parainfluenza virus?
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1. replicates in epithelial cells of the URT and can spread to LRT 2. IgE increases in pts with LRI; suggests hyperresponsiveness as the cause of symptoms |
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describe the type of immunity that develops after an infection with parainfluenza virus and whether one can be re-infected and get sick again |
Humoral and cell-mediated responses are protective, but transient.
Reinfection is common; infection induces temporary resistance to lower respiratory disease but protection persists < 1 yr and you still get the URI |
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How does croup present? What is the prodrome? Distinguishing feature(s)? |
URI prodrome |
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clinical manifestations of bronchiolitis |
cough, nasal discharge, and sometimes sudden apnea
Inflammatory obstruction of small airways, epithelial necrosis, mucous plugging, airway narrowing |
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1. Most common infectious cause of bronchiolitis? 2. Second most common? 3. What else can cause it |
1. RSV 2. parainfluenza 3 3. parainfluenza 1&2, adenovirus, influenza, mycoplasma, herpes |
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How is bronchiolitis diagnosed? |
clinical criteria with x-ray findings
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What are the xray findings in bronchiolitis? |
x-ray = hyperinflation, hyperlucency of the |
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management of bronchiolitis? |
hydration and supplemental O2 |
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1. Most common infectious cause of croup? 2. What else can cause it |
1. parainfluenza type 1&2 2. adenovirus, influenza, RSV, hMPV,enterovirus, rhinovirus, bacteria |
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Croup can be diagnosed clinically by what characteristic sign/symptom? What is seen on x-rays? |
1. Characteristic seal bark cough 2. Lateral neck film shows widening of the hypopharynx and narrowed subglottic airway. A-P films shows “steeple sign” of subglottic edema and narrowed airway. |
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management of croup? |
a. Humidification of air by nebulizer. |
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Transmission of RSV? |
human's = only reservoir
contaminated secretions is more important than airborne transmission (Cuddler Study). |
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Populations at risk for most serious infection with RSV? |
Premature babies and those with congenital heart disease or chronic lung disease. |
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Clinical manifestations in infants |
– Bronchiolitis – Pneumonia – Croup |
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Clinical manifestations in older children/adults |
– URI |
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Most common clinical manifestation of RSV? physical exam finding? |
Bronchiolitis = washing machine breath sounds |
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When does RSV typically occur during the year |
late fall to early spring
In temperate regions, RSV is highly seasonal with gradual onset and decline |
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How is RSV diagnosed in the lab? |
Rapid diagnosis using ELISA, PCR or direct fluorescent antibody test. PCR has become widely adopted. |
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pathophysiology of RSV? |
1. Infects an epithelial cell which causes the formation of a syncytium 2. The infection proceeds deeper into the respiratory tract collecting more debris/cells 3. This will eventually plug small airways = bronchiolitis |
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Pathologic changes with RSV likely result from _____ and ______ |
Pathologic changes with RSV likely result from direct viral infection and the host immune response. |
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Immunity after infection with RSV: humoral immunity? cellular immunity? re-infection? |
Cellular response halts established infection; humoral prevents recurrent disease.
repeated infection is common but usually only URI |
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Treatment of RSV |
• Mainly supportive |
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prophylactic treatment of RSV |
Palivizumab = Doesnt prevent infection prevents URI moving into LRI = prevents hospitalization
Humanized murine monoclonal antibody can be given intramuscularly, and is licensed for prophylaxis. |
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hMPV presents very similarly to |
RSV |
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Diagnosis of hMPV? |
Comprehensive Respiratory Platform for PCR now widely available in tertiary hospitals and reference laboratories |
