Podcast
Questions and Answers
Which aspect of the immune response to human para-influenza viruses (HPIV) primarily contributes to the development of hypoxemia and hypercarbia in young children?
Which aspect of the immune response to human para-influenza viruses (HPIV) primarily contributes to the development of hypoxemia and hypercarbia in young children?
- The production of IgE antibodies that lead to mast cell degranulation and bronchoconstriction.
- The release of viral RNA into the bloodstream, triggering systemic inflammation.
- The excessive mucus secretion and airway swelling induced by chemokines released from immune cells. (correct)
- The direct cytotoxic effect of natural killer cells on infected epithelial cells.
A 14-month-old child presents with a barking cough, inspiratory stridor, and a low-grade fever during late autumn. Which diagnostic finding would be most indicative of croup caused by HPIV-1 or HPIV-2, rather than a bacterial tracheitis?
A 14-month-old child presents with a barking cough, inspiratory stridor, and a low-grade fever during late autumn. Which diagnostic finding would be most indicative of croup caused by HPIV-1 or HPIV-2, rather than a bacterial tracheitis?
- Visualization of a 'steeple sign' on a neck X-ray, showing subglottic tracheal narrowing. (correct)
- Positive bacterial culture from a nasopharyngeal swab.
- Elevated white blood cell count with a left shift on a complete blood count.
- Diffuse alveolar infiltrates on a chest X-ray.
What is the most critical function of the F (fusion) protein in the pathogenesis of human para-influenza viruses (HPIV)?
What is the most critical function of the F (fusion) protein in the pathogenesis of human para-influenza viruses (HPIV)?
- To facilitate the attachment of the virus to sialic acid sugars on the host cell surface.
- To transcribe the negative-sense viral RNA into positive-sense mRNA strands within the host cell cytoplasm.
- To mediate the fusion of the viral envelope with the host cell membrane, enabling entry of the viral nucleocapsid. (correct)
- To cleave sialic acid residues, allowing the release of newly formed virions from the infected cell.
Why are children with a history of intubation considered to be at higher risk for severe para-influenza virus infections?
Why are children with a history of intubation considered to be at higher risk for severe para-influenza virus infections?
A child is diagnosed with bronchiolitis due to HPIV-3. Beyond supportive care, which intervention should be implemented to manage this condition?
A child is diagnosed with bronchiolitis due to HPIV-3. Beyond supportive care, which intervention should be implemented to manage this condition?
What is the underlying mechanism by which neuraminidase (NA) facilitates the spread of newly synthesized para-influenza viruses from an infected host cell?
What is the underlying mechanism by which neuraminidase (NA) facilitates the spread of newly synthesized para-influenza viruses from an infected host cell?
A 2-year-old child with a history of asthma presents with increased wheezing, chest congestion, and a persistent cough during an HPIV-3 outbreak. Which of the following interventions is MOST likely to prevent further complications?
A 2-year-old child with a history of asthma presents with increased wheezing, chest congestion, and a persistent cough during an HPIV-3 outbreak. Which of the following interventions is MOST likely to prevent further complications?
Which diagnostic method offers the MOST rapid and sensitive detection of human para-influenza virus (HPIV) RNA in a nasopharyngeal sample?
Which diagnostic method offers the MOST rapid and sensitive detection of human para-influenza virus (HPIV) RNA in a nasopharyngeal sample?
Following an infection with human para-influenza virus (HPIV), which of the following processes is directly responsible for increasing the permeability of blood vessels in the airway walls?
Following an infection with human para-influenza virus (HPIV), which of the following processes is directly responsible for increasing the permeability of blood vessels in the airway walls?
A researcher is studying the transmission dynamics of human para-influenza viruses (HPIV) in a daycare setting. Which intervention would be MOST effective in reducing the spread of HPIV among children?
A researcher is studying the transmission dynamics of human para-influenza viruses (HPIV) in a daycare setting. Which intervention would be MOST effective in reducing the spread of HPIV among children?
Flashcards
Human Para-Influenza Viruses (HPIV)
Human Para-Influenza Viruses (HPIV)
Viruses that commonly cause respiratory tract infections, especially in children; the second most common cause of acute respiratory infections in children under five.
Enveloped Virus
Enveloped Virus
A lipid membrane covering para-influenza viruses, enclosing a nucleocapsid with RNA genome and RNA polymerase enzyme.
H/N (Hemagglutinin-Neuraminidase)
H/N (Hemagglutinin-Neuraminidase)
Key glycoproteins on the lipid membrane of para-influenza viruses, facilitating viral entry and release.
F (Fusion Protein)
F (Fusion Protein)
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Croup (laryngotracheobronchitis)
Croup (laryngotracheobronchitis)
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Hypoxemia
Hypoxemia
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Hypercarbia
Hypercarbia
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Inspiratory Stridor
Inspiratory Stridor
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Steeple Sign
Steeple Sign
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RT-PCR, Immunofluorescence, Viral Culture
RT-PCR, Immunofluorescence, Viral Culture
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Study Notes
- The key elements associated with the influenza viruses are aerosols, hemagglutinin and neuraminidase, glycoprotein fusion, and glycoprotein croup.
- Children with influenza can develop conditions such as bronchiolitis and pneumonia.
Human Para-Influenza Viruses (HPIV)
- HPIVs are a common cause of respiratory tract infections, especially in children.
- HPIVs are the second most common cause of acute respiratory infections in children under five years old.
- There are four types of HPIVs that infect humans: types 1, 2, 3, and 4.
- HPIVs belong to the Paramyxoviridae family.
Structure
- HPIVs are enveloped viruses, meaning they are covered by a lipid membrane.
- Inside the lipid membrane is a nucleocapsid containing a single-stranded, negative-sense RNA genome and an RNA polymerase enzyme.
- The lipid membrane features hemagglutinin-neuraminidase (H/N) and fusion (F) glycoproteins.
Transmission
- HPIVs spread through virus-containing droplets released when an infected person coughs or sneezes which can reach up to 2 meters (6 feet) away.
- These droplets can be inhaled or land in the mouths or noses of people nearby.
- The virus can survive on surfaces for a few hours, spreading through contact with contaminated surfaces.
Pathogenesis
- Hemagglutinin binds to sialic acid sugars on respiratory tract epithelial cells, initiating infection.
- The fusion (F) protein helps the virus fuse with the epithelial cell membrane, releasing the nucleocapsid into the cytoplasm.
- RNA polymerase transcribes the negative-sense viral RNA into positive-sense mRNA strands within the cytoplasm.
- Host cell ribosomes translate mRNA strands into viral proteins, which assemble into new viruses.
- Neuraminidase cleaves sialic acid sugars, facilitating the release of new viruses from the cell membrane to infect neighboring cells.
- The virus destroys epithelial cells, triggering an immune response, which causes inflammation and increased mucus secretion.
- Blood vessels in the airway walls become more permeable, leading to airway swelling.
Why Children Are More Affected
- Children's airways are narrower than adults.
- Inflammation and swelling can lead to hypoxemia (low blood oxygen levels) and hypercarbia (high blood carbon dioxide levels).
Diseases Caused by HPIV
- HPIV-1 and HPIV-2 commonly cause croup (acute laryngotracheobronchitis). Croup is the inflammation of the larynx, trachea, and bronchi.
- HPIV-3 commonly affects the lower airways, causing pneumonia or bronchiolitis. Bronchiolitis is the inflammation of the bronchioles.
- HPIV-4 affects both upper and lower respiratory tracts, with infections being rare and mild.
Epidemiology and Risk Factors
- Para-influenza outbreaks occur more frequently in late autumn.
- High-risk populations include children 6 months to 3 years old, people with congenital airway narrowing, people with hyperactive airways such as those with asthma as well as people with a history of intubation.
Symptoms
- The incubation period is 2 to 6 days.
- Early symptoms include abdominal pain, myalgia (muscle pain), fatigue, headaches, and fever.
Symptoms Specific to Each Disease
- Croup (HPIV-1, HPIV-2) symptoms: inspiratory stridor (high-pitched breathing noise), laryngeal obstruction, barking cough, and hoarse voice. Severe croup can cause agitation due to hypoxia.
- Bronchiolitis (HPIV-3) symptoms: chest congestion, sore throat, cough, and wheezing.
- Pneumonia (HPIV-3, HPIV-4) symptoms: shortness of breath, chest pain, and a productive cough that may include pus or blood in sputum.
Diagnosis
- Nasopharyngeal secretions are collected via nasal/throat swabs or nasal aspiration for diagnosis.
- Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) detects tiny amounts of viral RNA.
- Immunofluorescence or ELISA detects viral antigens.
- Viral culture grows the virus in a culture medium.
- A neck X-ray in croup shows tracheal narrowing, forming a "steeple sign".
- A chest X-ray in pneumonia may show pulmonary consolidation.
Treatment
- Most para-influenza infections are self-limiting, only requiring antipyretics to reduce fever.
- Moderate to severe croup is treated with corticosteroids such as dexamethasone, to reduce airway inflammation; racemic epinephrine nebulization is given if corticosteroids are ineffective.
- Bronchiolitis is treated with supplemental oxygen and IV fluids to prevent dehydration.
Prevention
- Currently, there is no vaccine for para-influenza viruses.
- Best prevention methods include covering the mouth while sneezing/coughing, proper handwashing, sanitizing surfaces, and avoiding close contact with infected individuals.
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