Orthomyxoviruses and Influenza Quiz
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Questions and Answers

Which of the following is a characteristic symptom of croup in young children?

  • High fever and chills
  • Excessive mucus production
  • A cough resembling a barking seal (correct)
  • Wheezing during exhalation

    • Which laboratory method is used to detect influenza viral RNA?

  • Western blot
  • Gram staining
  • ELISA
  • RT-PCR (correct)

    • What immunological factor correlates with protection against influenza?

  • Cell-mediated cytotoxicity
  • Serum antibodies and secretory IgA (correct)
  • Antibodies against the matrix protein
  • Antibodies against the ribonucleoprotein

    • Why are influenza vaccines updated annually?

    <p>To match circulating strains of the virus (A)</p> Signup and view all the answers

    Which of the following is a key characteristic of Reye Syndrome?

    <p>An acute encephalopathy primarily affecting children and adolescents (B)</p> Signup and view all the answers

    Which viral family includes viruses characterized by their segmented RNA genome?

    <p>Orthomyxoviridae (C)</p> Signup and view all the answers

    Which of the following is a key area of focus when studying orthomyxoviruses?

    <p>Viral properties, biological properties, and antigenic structure (B)</p> Signup and view all the answers

    Which viral characteristic is most relevant for understanding the epidemiology and evolution of Orthomyxoviruses?

    <p>Antigenic structure (C)</p> Signup and view all the answers

    In the context of viral infections, what does 'biological properties' primarily refer to?

    <p>The virus's mechanism of transmission and its interaction with host cells (A)</p> Signup and view all the answers

    What is a distinguishing feature of Paramyxoviruses compared to other viral families?

    <p>Single-stranded RNA genome (A)</p> Signup and view all the answers

    Which characteristic distinguishes orthomyxoviruses at the protein level?

    <p>The specific matrix protein (M) and nucleoprotein (NP). (C)</p> Signup and view all the answers

    What replication characteristic is unique to orthomyxoviruses compared to other RNA viruses?

    <p>Transcription occurs within the nucleus. (D)</p> Signup and view all the answers

    What structural feature of the orthomyxovirus genome contributes most significantly to its ability to undergo antigenic shift?

    <p>The segmented nature of its RNA. (B)</p> Signup and view all the answers

    Antigenic drift in influenza viruses is primarily the result of what type of genetic change?

    <p>Point mutations in glycoprotein genes (D)</p> Signup and view all the answers

    Which influenza virus type does not undergo antigenic shift?

    <p>Both B and C (C)</p> Signup and view all the answers

    Which component is included when naming influenza virus isolates?

    <p>Geographic origin (B)</p> Signup and view all the answers

    What do the parentheses in the nomenclature of influenza A viruses indicate?

    <p>Antigenic descriptions of hemagglutinin (HA) and neuraminidase (NA). (C)</p> Signup and view all the answers

    Why are orthomyxoviruses considered zoonotic infections?

    <p>They are carried by birds and mammals and can transmit to humans (D)</p> Signup and view all the answers

    Which characteristic contributes most to the spread and infectivity of paramyxoviruses, despite their fragile nature?

    <p>High infectivity despite the particles' lability. (C)</p> Signup and view all the answers

    What is the primary composition, by percentage, of a paramyxovirus virion?

    <p>Protein (73%), lipid (20%), carbohydrate (6%), RNA (1%) (C)</p> Signup and view all the answers

    Which of the following is NOT a recognized characteristic of paramyxoviruses?

    <p>Virion size is typically less than 50 nm in diameter. (A)</p> Signup and view all the answers

    Which of the following statements accurately describes the epidemiology of parainfluenza viruses (HPIV) in young children?

    <p>Type 3 is most prevalent, with the majority of infants infected during their first year of life. (B)</p> Signup and view all the answers

    What is the function of the glycoprotein found in the envelope of paramyxoviruses?

    <p>To attach to host cells and mediate fusion. (A)</p> Signup and view all the answers

    Which of the following characteristics of paramyxoviruses contributes to their classification?

    <p>Whether they contain hemagglutinin or neuraminidase activity. (B)</p> Signup and view all the answers

    Which factor is least likely to predispose young children to paramyxovirus infections?

    <p>Adequate vitamin A intake (C)</p> Signup and view all the answers

    Which characteristic makes it more difficult to develop a broadly effective vaccine against all paramyxoviruses?

    <p>The antigenic stability of the viruses. (A)</p> Signup and view all the answers

    In immunocompetent hosts, parainfluenza virus replication is typically confined to which area?

    <p>Respiratory epithelia (D)</p> Signup and view all the answers

    Which factor does NOT significantly influence the severity of parainfluenza virus infection?

    <p>Patient's ABO blood type (B)</p> Signup and view all the answers

    Parainfluenza virus types 1 and 2 are most commonly associated with causing which illness in young children?

    <p>Laryngotracheitis and croup (B)</p> Signup and view all the answers

    During RSV epidemics, what is the likely mode of transmission to families?

    <p>Infected Schoolchildren (C)</p> Signup and view all the answers

    How does RSV spread within the respiratory system?

    <p>Extracellularly and by fusion of cells to form syncytia (A)</p> Signup and view all the answers

    What is the typical incubation period (IP) for RSV?

    <p>3-5 days (A)</p> Signup and view all the answers

    In what population does pneumonia develop in approximately half of RSV infected cases?

    <p>Immunocompromised children and adults (C)</p> Signup and view all the answers

    Following RSV bronchiolitis or pneumonia as infants, children often experience what recurrent symptom?

    <p>Recurrent episodes of wheezing illness (B)</p> Signup and view all the answers

    In cases of RSV infection superimposed on a preexisting condition like congenital heart disease, what is a likely outcome?

    <p>The mortality rate may be high. (B)</p> Signup and view all the answers

    What role does RSV play in the context of ear infections?

    <p>RSV is an important cause of otitis media. (C)</p> Signup and view all the answers

    Which of the following methods is suitable for the laboratory diagnosis of RSV?

    <p>RT-PCR (A)</p> Signup and view all the answers

    What is the primary focus of treatment for RSV infections?

    <p>Supportive care, such as administration of oxygen (B)</p> Signup and view all the answers

    Which of the following is true regarding mumps virus?

    <p>It occurs only in a single serotype and shares minor common envelope antigens with other Paramyxovirus species. (A)</p> Signup and view all the answers

    What is a characteristic of mumps epidemiology?

    <p>Mumps occurs worldwide and outbreaks can occur in institutions. (B)</p> Signup and view all the answers

    How does the mumps virus initially enter the body?

    <p>Through the pharynx or conjunctiva. (A)</p> Signup and view all the answers

    Approximately when does shedding of the mumps virus begin in relation to the onset of symptoms?

    <p>About 6 days before symptoms appear. (A)</p> Signup and view all the answers

    Flashcards

    Orthomyxovirus

    A family of RNA viruses that includes influenzaviruses, known for causing influenza.

    Viral properties

    Characteristics of viruses such as structure, size, and life cycle.

    Biological properties

    Attributes of viruses that affect their interactions with host cells and the immune system.

    Antigenic structure

    The specific arrangement of antigens on a virus that triggers immune responses.

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    Paramyxoviruses

    A family of viruses that includes those causing diseases like mumps and measles; related to Orthomyxoviruses.

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    Croup symptoms

    Cough resembling a barking seal, difficulty breathing, and stridor in young children.

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    Reye Syndrome

    Acute encephalopathy in children aged 2-16, linked to certain viral infections.

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    Immunity to influenza

    Long-lived, subtype-specific protection correlating with serum antibodies and secretory IgA.

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    Influenza vaccines

    Annually updated vaccines targeting specific circulating strains, including inactivated and live attenuated types.

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    Laboratory diagnosis of influenza

    Involves detecting viral RNA, virus isolation, and serology using various methods like RT-PCR and ELISA.

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    Epidemiology of Influenza

    Study of how influenza viruses spread, often as zoonotic infections from birds and mammals.

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    Antigenic Drift

    Gradual changes in viral antigens due to point mutations, allowing escape from immune detection.

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    Antigenic Shift

    Abrupt antigenic change from genetic reassortment between different virus strains.

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    Influenza Virus Structure

    Influenza viruses are spherical, enveloped particles with RNA genome and helical nucleocapsid.

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    Genetic Reassortment

    Process where segmented RNA genome of a virus can mix with other strains, leading to new virus strains.

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    Nomenclature of Influenza Viruses

    System used to identify influenza viruses based on type, host, origin, strain, and year.

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    Antigenic Stability of Type C

    Influenza type C shows little antigenic variation, making it more stable than A and B.

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    Antiviral medication

    Medications used to treat or prevent viral infections.

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    Neuraminidase Inhibitors

    A class of antiviral drugs that block viral replication by inhibiting neuraminidase enzyme.

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    Endonuclease Inhibitors

    Antivirals that inhibit endonuclease, affecting viral RNA transcription.

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    Characteristics of Paramyxoviruses

    Spherical particles, RNA composition, and fragile envelope.

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    Epidemiology of Paramyxoviruses

    Type 3 is the most prevalent, affecting young children prominently.

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    Classification of Paramyxoviridae

    Divided into two subfamilies and seven genera, with human pathogens in six genera.

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    Predisposing factors for infections

    Conditions like malnutrition and overcrowding that increase infection risk.

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    Parainfluenza Virus

    A virus that primarily affects respiratory epithelia and causes infections in young children.

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    Syncytia Formation

    A process where virus-infected cells fuse, forming multinucleated giant cells.

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    Bronchiolitis

    A clinical syndrome resulting from viral infection, especially in infants.

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    Viremia

    The presence of viruses in the bloodstream.

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    IgE Antibodies

    Immunoglobulins implicated in allergic reactions and associated with disease severity.

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    Croup

    A respiratory condition characterized by a barking cough, often due to parainfluenza virus types 1 and 2.

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    Respiratory Tract Infection

    An infection affecting the upper or lower respiratory tract, caused by various pathogens.

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    Reinfections

    Subsequent infections by the same virus, common in both children and adults.

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    Superimposed Infection

    An infection that occurs on top of an existing disease, increasing mortality risk.

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    RSV Complications

    Respiratory Syncytial Virus (RSV) is a key cause of ear infections (otitis media).

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    Laboratory Diagnosis of RSV

    RT-PCR and viral antigen detection are methods for diagnosing RSV; hemagglutination cannot be used.

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    RSV Treatment

    Treatment is mainly supportive; Ribavirin may be used for high-risk infants.

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    Mumps Virus Characteristics

    Mumps is classified as a single serotype and shares minor antigens with other paramyxoviruses.

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    Mumps Epidemiology

    Mumps is found globally, peaking in winter and spring, primarily affecting humans in close communities.

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    Mumps Virus Entry

    The virus enters through the pharynx or conjunctiva, leading to primary viremia.

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    Virus Shedding in Mumps

    Virus shedding starts about 6 days before symptoms and lasts for 5 days, occurring in saliva and urine.

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    Study Notes

    Orthomyxoviruses and Paramyxoviruses

    • Orthomyxoviruses include influenza viruses.

    • These viruses are distributed worldwide and originate as zoonotic infections transmitted by various bird and mammal species.

    • Two major proteins, matrix protein (M) and nucleoprotein (NP), distinguish these viruses.

    • Influenza viruses have a spherical, pleomorphic virion (80-120nm in diameter) with a helical nucleocapsid.

    • They have an RNA genome (single-stranded, segmented, negative-sense, 13.6kb).

    • The viral composition includes RNA, protein, lipid, and carbohydrates (1%, 73%, 20%, and 6% respectively).

    • Influenza viruses have nine structural proteins and one non-structural protein.

    • The envelope contains viral hemagglutinin and neuraminidase proteins.

    • Replication occurs in the nucleus via transcription, and particles mature through budding from the plasma membrane.

    • A unique characteristic is genetic reassortment among members of the same genus.

    • Influenza A viruses undergo antigenic shift (abrupt change) caused by genetic reassortment with unrelated strains.

    • Antigenic drift (gradual change) is caused by point mutations affecting the glycoprotein's antigenic sites.

    • Several influenza A subtypes (e.g., H1N1, H2N2, H3N2, H1N1) have been identified, and they result in yearly and pandemic outbreaks.

    • Influenza B and C viruses exhibit antigenic drift but not shift, as few related viruses exist in animals.

    • Paramyxoviruses include important respiratory infection agents for infants and young children.

    • Two common childhood diseases are caused by this virus: Mumps and Measles.

    • WHO estimates that acute respiratory infections and pneumonia cause the death of four million children under five annually worldwide.

    • Paramyxoviruses have a spherical, pleomorphic virion (120-300nm in diameter) with a helical nucleocapsid.

    • This virus' composition includes RNA (1%), protein (73%), lipid (20%), and carbohydrates (6%).

    • The virus’ genome is single-stranded, linear, non-segmented, and negative-sense RNA.

    • Six to eight structural proteins are present.

    • The envelope contains viral glycoproteins, (G, H, or HN) associated with hemagglutinin or neuraminidase activity and fusion protein.

    • The virus replicates in the cytoplasm and buds from the plasma membrane.

    • They are antigenically stable but labile. Their highly infectious nature is apparent.

    • Includes subfamilies, genera, and species.

    • Parainfluenza viruses, Rubulaviruses, Morbillivirus, and Pneumoviruses all fall under this group.

    • Parainfluenza viruses cause respiratory infections, and sub-types exist for these viruses.

    • Infections with specific types and strains cause varying degrees of disease.

    Classification and Nomenclature

    • Orthomyxoviruses belong to the Orthomyxoviridae family, and the genus consists of influenza types A, B, and C.
    • Classification is based on variation in the nucleoprotein antigen.
    • Influenza types A and B have variable hemagglutinin and neuraminidase antigens, which undergo genetic variation and are the basis for new strains.
    • Type C influenza is antigenically stable.
    • The nomenclature specifies the type, host of origin, geographic origin, strain number, and isolation year.
    • Antigen descriptions (HA and NA) are put in parentheses.
    • The host origin is excluded from human isolates.
    • Several subtypes of HA and NA have emerged and continue to be observed.
    • Paramyxoviruses belong to the Paramyxoviridae family and are divided into two subfamilies with seven genera.
    • Classification is based on characteristics evident in their species and types.

    Epidemiology

    • Annual influenza outbreaks cause 3 to 5 million severe illnesses and 250,000 to 500,000 deaths worldwide.

    • Influenza incidence peaks in winter.

    • Influenza C is mild and sporadic.

    • Yearly epidemics are both types A and B.

    • Pandemic influenzal outbreaks are the result of type A viruses.

    • Paramyxovirus infections are a significant cause of lower respiratory tract disease in young children.

    • Type 3 Parainfluenza is the most prevalent infection.

    • Type 3 Parainfluenza infections peak within the first year of life, and occur during the fall or winter for Types 1 and 2.

    • Several factors such as malnutrition, overcrowding, vitamin A deficiency, and environmental toxins can cause outbreaks.

    Pathogenesis

    • Influenza viruses are transmitted by droplets from sneezing or coughing.

    • The virus enters the lower respiratory tract (where the tracheobronchial tree is involved along with the nasopharynx).

    • Viral neuraminidase acts upon the N-acetylneuraminic acid within mucus, leading to liquefaction.

    • The liquefied mucus aids in transmitting the virus throughout the respiratory system.

    • Viral infection of mucosal cells results in cell destruction and desquamation of the superficial mucosa.

    • Parainfluenza viruses cause limited replication in respiratory epithelia and seldom cause viremia.

    • Disease severity is influenced by the susceptibility of viral proteins to proteases.

    • Protease production by host cells and patient immune response, along with airway reactivity, impacts disease severity.

    • RSV infection initially affects the nasopharynx’s epithelial cells.

    • Virus spreads through extracellular and intracellular pathways forming syncytia, possibly affecting the lower respiratory tract and causing bronchiolitis or pneumonia.

    • Viremia may or may not occur.

    • Narrow airways are more prone to obstruction from inflammation and edema.

    • Viral shedding varies from 1-3 weeks in infants/children to 1-2 days in adults.

    Clinical Findings

    • Uncomplicated influenza involves fever (38-40°C), myalgia, headache, ocular symptoms, and a dry cough with nasal discharge.

    • H1N1 may also cause gastrointestinal distress

    • Viral complications in young children can cause croup, which involves cough that sounds like barking, difficulty breathing, stridor (the creaking sound when breathing).

    • Pneumonia as a complication primarily occurs in elderly adults or those with severe illnesses. It may be of viral, bacterial, or mixed origin.

    • Reye syndrome, a severe encephalopathy, is a rare complication associated with influenza B or A, or with varicella-zoster viral infections.

    • Parainfluenza commonly causes rhinitis, pharyngitis, and bronchitis in infants, leading to serious illnesses like laryngotracheitis and croup for types 1 and 2.

    • Bronchiolitis and pneumonia are typical complications of type 3 parainfluenza infections.

    • RSV ranges from a common cold to pneumonia or bronchiolitis.

    • Children who have experienced RSV bronchiolitis or pneumonia in infancy frequently present with recurrent wheezing due to recurrent infections.

    • Mumps is marked by painful parotid gland swelling and sometimes submandibular gland swelling or swelling in the testes or ovaries.

    • Meningitis may be a related viral infection affecting the central nervous system.

    Immunity

    • Influenza immunity is long-lasting and subtype-specific.

    • Immunity correlates with serum antibodies and secretory IgA.

    • Antibodies against the ribonucleoprotein are type-specific and aid in typing isolates.

    • Natural infection generates IgA antibodies in nasal secretions that confer resistance to reinfection.

    • Antibody response to reinfection often becomes less specific.

    Laboratory Diagnosis

    • Influenza viral RNA can be detected using RT-PCR.

    • Virus isolation is possible using embryonated eggs or primary monkey kidney cells, and viral antigens are diagnosed by fluorescent or enzymatic immunoassays.

    • Serology through complement fixation, hemagglutination inhibition, immunodiffusion, or ELISA detects antibodies.

    • Typical specimens include nasal washings, gargles, and throat swabs.

    • Paramyxovirus diagnosis is similar, with nucleic acid detection, viral antigen detection, isolation of the virus (using suitable cell lines), and serology methods.

    Prevention and Treatment

    • Inactivated and live-attenuated influenza vaccines are used for prevention, updated annually to match circulating strains.

    • Antiviral medications, such as neuraminidase inhibitors (e.g., oseltamivir, zanamivir, peramivir) and endonuclease inhibitors (e.g., baloxavir marboxil), are used for treatment and/or prophylaxis.

    • Parainfluenza prevention includes contact isolation precautions to control nosocomial outbreaks.

    • Ribavirin is used to treat serious cases in immunocompromised patients.

    • RSV lacks a vaccine.

    • Supportive care, such as oxygen, and secretion removal, is typically utilized in cases of severe respiratory illnesses (with Ribavirin, an antiviral, being occasionally administered in high-risk patients).

    • Mumps prevention relies on the MMR (measles-mumps-rubella) vaccine, which is now widely available and recommended.

    • No specific therapy exists for mumps, prevention is the most important tool for controlling its spread.

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    Description

    Test your knowledge on Orthomyxoviruses, their characteristics, and their association with influenza. This quiz covers symptoms of croup in children, detection methods for influenza, and the relevance of annual vaccine updates. Dive deep into the immunological factors and unique replication features of these viruses.

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