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» OCW Home » Microbiology » Student Notes 
Lecture 22 - Respiratory Viruses
Author: Amelia Virostko

1. General Concepts

  1. Variation in severity depends on age, previous infection, and immune status
  2. Specific viruses associated with specific syndromes and seasonal variation
  3. Routes of transmission are from contaminated secretions or aerosol ingestion

2. Influenza Virus

  1. 6th leading cause of death
  2. Hemagglutinin: stick to receptors on respiratory epithelial cells
  3. Neuraminidase: eats away neighbor receptors decreasing the number of times other virions can affect the same cell
  4. Vaccine is a mix of hemagglutinin and neuraminidase protein
  5. Replicative cycle: adsorption --> penetration --> uncoating --> traverse membrane --> replication --> hemagglutinin and neuraminidase made --> viral assembly --> hemagglutinin and neuraminidase inserted --> virus buds off
  6. Signs and symptoms of influenza: fever above 100 degrees, non-productive cough, chills and/or sweats, headache, myalgia, sore throat, malaise, substernal soreness, photophobia, and ocular problems
  7. Complications: pneumonia, exacerbation of asthma, myocarditis, pericarditis, meningitis, encephalitis, Reye syndrome, Guillain-Barre syndrome, myositis, myoglobinuria
  8. Peak influenza activity in January and February
  9. Antigenic drift: minor change in antigenicity due to mutations in genes coding for hemagglutinin or neuraminidase
  10. Antigenic shift: acquisition of new gene coding for hemagglutinin or neuraminidase
  11. Control influenza with vaccination, treatment and prophylaxis with antiviral agents
  12. Treatment
    1. M2 (only found on Influenza A) inhibitors: amantadine and rimantadine
    2. Neuraminidase inhibitors: zanamivir and oseltamivir
    3. Shorten illness by 1.5 days when used for treatment

3. Adenovirus

  1. Can cause pharyngitis, pneumonia, pertussis-like syndrome, keratoconjunctivitis, meningoencephalitis, gastroenteritis

4. Parainfluenza Viruses

  1. Types I and II cause fall epidemics
  2. Type III is endemic
  3. Causes croup, pneumonia, and bronchiolitis

5. Rhinovirus

  1. Picornavirus with >100 serotypes
  2. No cross protection between strains
  3. Spring, autumn peak activity
  4. Causes common cold with potential sinusitis, otitis media, and asthmatic bronchitis complication

6. Coronavirus

  1. Cause of upper respiratory infection and rarely lower respirator tract illness
  2. Respiratory spread from person to person
  3. Accounts for 15% of adult upper respiratory illnesses
  4. Identified as agent of SARS

7. Respiratory Syncytial Virus

  1. #1 cause of hospitalization in first year of life
  2. By 2 years of age, 100% of individuals infected
    1. In most, infection confined to upper respiratory tract and does not cause bronchiolitis (cannot get oxygen in and out of alveoli) B. 0-2 months: apneic spells
  3. 2-24 months: cough, rhinorrhea, wheezes, tachypnea
  4. >2 years: acute asthmatic bronchitis
  5. Adults: fever, cough, rhinorrhea

8. Human Metapneumovirus

  1. Disease similar to RSV
  2. Most children seropositive by 5 years of age
  3. Causes approximately 10% of wintertime unexplained respiratory illnesses
  4. Recurrent infection later in life
  5. Bronchiolitis, croup, asthma, and pneumonia exacerbations
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