10-29-b- Viral Respiratory Tract Infections Part I.txt

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10-29-b- Viral Respiratory Tract Infections Part I.txt
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  1. 10-29-b: Viral Respiratory Tract Infections Part I
    • Respiratory infections are the #1 cause of outpatient visits in the US
    • Most are just a nuisance but often can be serious or fatal (extreme cas is hantabirus pulmonary syndrome > 50% fatality
    • Role of vaccines
  2. Types of Respiratory Infections
    • Upper respiratory Infections: sinusitis, common cold, pharyngitis, epiglottitis, laryngotracheitis
    • Loser respiratory infections: bronchitis, bronchiolitis, pneumonia – can sometimes be fatal
    • The lower you go, the more serious it gets
  3. Common cold
    • Rhinoviruses
    • Coronaviruses
    • These two probably represent 80% or common cold infections, Rhino to Corona 4:1
  4. Pharyngitis and tonsillitis
    Begin to have bacteria as a large number of causes as well as viruses
  5. Pneumonia
    A lot of bacteria, viruses, as well as fungi
  6. What contributes to disease symptoms in viral pathogenesis?
    • Cell Killing and Immunopathology: respiratory epithelium, etc.
    • Response to flu is to generate a cytokine floow, IL-1 fever
  7. The Common Cold: Symptoms
    Scratchy throat, nasal discharge, malaise, headache, cough; 1-2 day incubation period, no fever
  8. Common cold: pathogenesis:
    • infection of respiratory epithelium
    • ciliary action stops
    • mucous secretion increases
    • inflammaroty reaction
    • infection stopped by IFN and antibodies
  9. Common cold: epidemiology
    • Inhalation of infected droplets
    • Infected mucous transfer to nose or eye
    • Children initiate outbreaks due to poor hygiene
    • Fomites
  10. Common cold: prevention and treatment
    • Hand washing
    • Avoid people with colds
    • Symptomatic
  11. Rhinovirus
    • Principal common cold virus
    • Many different serotypes, makes vaccine development difficult
    • But days of work lost because of symptoms
    • Unenveloped; 4 structure proteins, VP1 important:
    • Mimicking ICAM-1or the viral attachment site can prevent binding of virus to cell and prevent infection
    • Can also target a protease that chops up the proteins into usable components that allow replication; if block protease, as in HIV as well, then block viral replication
  12. Epidemiology of Rhinovirus Infections
    • Resistant to drying and detergents
    • Replication best at 33C
    • Everyone at risk
    • Worldwide, usually in winter
  13. Adenovirus
    • Not a major cause of common colds:
    • Associated with pharyngitis and a range of other diseases, including som serious lower RIs
    • NOT enveloped: knobs on the virus allow interactions, many treatment prevent interactions of those knobs with the cel
    • Relatively cell-independent virus, so can also target early gene production to prevent replication.
  14. Diseases caused by adenoviruses
    • Able to cause a wide range of disease b/c can infect many different organs, unlike rhinovirus – only respiratory tract cells
    • Endemic respiratory disease:
    • Acute respiratory disease of military recruits: can be fatal
    • Pneumonia:
    • Pharyngoconjunctival fever: eye attacked
    • Keratoconjunctivitis: eye
    • Less common include: gastroenteritis, pertussis-like syndrome, hepatitis, acute hemorrhagic cystitis, etc.
  15. Disease mechanisms of adenoviruses
    • Spread by: aerosol, close contact,or fecal-oral means to establish pharyngeal infection, fingers spread to eyes
    • Virus infects: mucoepithelial cells in the respiratory tract, GI tract, and conjuctive or cornea, causing cell damage directly
    • Virus persists: in lymphoid tissue (e.g. tonsils, adenoids, Peyer’s patches)
    • Antibody – important tof prophylaxis and resolution
  16. Epidemiology of Adenoviruses
    • Resistant to drying and GI tract (chlorine in pools)
    • Asymmptomatically shed
    • Day-care centers, military traning camps
    • Worldwide, all seasons
    • Live vaccine for military use
  17. Other issues for Adenoviruses
    • Viral pharyngitis (including adeno) can resemble strep throat
    • Throat swab – rapid Ag test for strep; PCR for viruses
    • Adenoviruses are popular vehicles for gene therapy
  18. Coronaviruses
    • Second most common cause of colds
    • Also cause GI tract infections and SARS
    • Positive-stranded virus
  19. Coronavirus disease mechanisms
    • Infects epithelial cells of upper respiratory tract
    • Enveloped virus is able to survive the GI tract
    • Reinfection occurs in presens of serum antibodies
  20. SARS ( Severe Acute Respiratory Syndrome)
    • Guangdong province, PRC, Nov 2002
    • Flu-like symptoms+diarrhea
    • 20% of overall fatality
    • New corona virus: SARS CoV
    • Source horseshoe bats (rhinolophidae species): source reservour for the virus
    • Classic zoonosis
  21. SARS – last group of cases
    • In April 2004 when 9 people were diagnosed; linked to virology lab
    • Who should be watched carefully?
    • People with radiologically confirmed pneumonia, and a risk factor (visit to far east, hospital/lab contact):
  22. Human metapneumovirus
    • Recently-discovered paramyxovirus (2001)
    • In Holland, 100% seroconversion by age 5
    • Causes mild or severe URT and LRT infections in all age groups (particularly the elderly)
    • Clinically similar to Respiratory Syncytial Virus (5-15 % of bronchiolitis in infants)
  23. Recent U.D. study suggests about 6% of children in tertiary care setting have hMPV
    • 12-15% of LRT (e.g. bronchiolitis) and URT infections in children may be due to the virus
    • Complicates RSV infection and found in conjunction with HIV, too. (dual infections)
    • Now found worldwide
    • Serious enough to warrant vaccine development

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