To know the viruses that are a major cause of acute repiratory disease (ard)




Дата канвертавання18.04.2016
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Medical Microbiology & Immunology

Lecture 20 Virology Respiratory viruses




  1. To know the viruses that are a major cause of acute repiratory disease (ARD).

    Virus

    Classification

    Morphology

    Genome

    Influenza

    Orthomyxoviridae

    Enveloped, helical

    ss(-)RNA segment

    Parainfluenza

    Paramyxoviridae

    Enveloped, helical

    ss(-)RNA

    Respiratory syncytial virus

    Paramyxoviridae

    Enveloped, helical

    ss(-)RNA

    Adenoviruses

    Adenoviridae

    Icosahedral

    dsDNA

    Rhinoviruses

    Picornaviridae

    Icosahedral

    ss(+)RNA

    Coronaviruses

    Coronaviridae

    Enveloped, helical

    ss(+)RNA

  2. To describe the unique characteristics of each viral group, including structure and mode of replication.

    Viral group

    Structure

    Mode of replication

    Orthomyxoviridae

    Type A – 8 seg. ssRNA

    Type B – 8 seg. Type C – 8 seg.

    Nucleoprotein covers RNA to form ribonucleoprotein complex, surrounded by matrix, envelope contains hemagglutinin and neuraminidase glycoprotein spikes, pleomorphic


    Adsorption mediated by H, uncoating in the cytoplasm, replicates in the nucleus, nucleocapsid assembles, and virus buds through nuclear membrane where matrix has accumulated.

    Paramyxoviridae

    Parainfluenza Virus



    4 stable serotypes - single-stranded (-) RNA, nucleoprotein covers RNA, M protein surrounds nucleoprotein complex, envelope contains attachment protein that has both H and N and the fusion protein (F), pleomorphic

    Replication occurs in the cytoplasm, replicates like (-) RNA virus, and buds through cytoplasmic membrane.

    Paramyxoviridae

    Respiratory Syncytial Virus



    2 serotypes (A and B), classified as Pneumovirus

    same structure as parainfluenza virus except envelope glycoproteins are an attachment (G) and a fusion (F)



    Same as parainfluenza virus.

    Adenoviridae

    47 serotypes infect humans, naked capsid virus (icosahedral), ds linear DNA

    Replication and assembly occur in the nucleus virions are released by cell destruction

    Picornaviridae

    About 115 serotypes 20 to 30 nm, (+) ss RNA, cubic, naked

    Optimum growth at 33°C

    Coronaviridae

    (+) ss RNA, helical enveloped

    Replicate in cytoplasm, buds through endoplasmic reticulum or Golgi

    Reoviridae

    4 serotypes, dsRNA, segmented, small icosahedral, naked




  3. To explain the clinical disease(s) associated with each virus. See question 4.

  4. To discuss the diagnosis, treatment and prevention of respiratory infections.

Viral group

Clinical disease

Diagnosis

Treatment and prevention

Orthomyxoviridae

30,000 deaths per year in US, incubation 1-2 days, abrupt onset of fever, myalgia, headache, muscle ache, chills, cough and fatigue (5-7 days), followed by prolonged cough (2+ weeks), possible pneumonia (risk factors – age, heart, and lung defects)

Clinical picture, isolate virus in cell culture and serology (antibody titer to H)

Treatment: supportive; Amantadine and Riamantadine (early), new drugs Zanamivir and Oseltamivir (+ for prophylaxis)

Prevention: killed vaccine, drugs (above)



Paramyxoviridae

Parainfluenza Virus



Parainfluenza 1: major cause of acute croup.

Parainfluenza 2: croup in kids

Parainfluenza 3: severe bronchitis and flash for pneumonia in infants <1 year.

Parainfluenza 4: least common RUI



Clinical picture, serology, virus isolation

Treatment: no specific treatment or prevention

Paramyxoviridae

Respiratory Syncytial Virus



Most important bronchiolitis and pneumonia in infants <1 year, acute phase of cough, wheezing, and respiratory distress (1-3 weeks). Fatality: 0.5-1.0%

Immunofluorescence (nasal secretions)

Treatment: supportive (aerosol ribavirin)

Prevention: no vaccine, nasal spray vaccine underdevelopment



Adenoviridae

Subclinical latent infection (days-years), febrile childhood disease, pharyngoconjunctival fever, conjunctivitis, cystitis, gastroenteritis, pertussis-like (whooping cough).

Isolate virus (confusing because of healthy carriers), clinical picture

Treatment: supportive

Prevention: enteric coated live vaccine



Picornaviridae

Common cold syndrome, no fever, sneezing, congestion, nasal secretions, short duration (2-4 days)

Clinical picture

No treatment, no prevention

Coronaviridae

Common cold syndrome

10% of winter colds



Clinical picture

Kleenex (antiviral), no vaccines, new drug BIRR-4 (nasal spray) reduces severity 50%

Reoviridae

Asymptomatic (mostly)

Difficult - clinical picture

None


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