Independent Study: Upper Respiratory Tract Infections

What is being described:

• Viral infection of upper respiratory tract.

• Most common respiratory tract infection

• Most adults have 3-4 colds/year; school-age children may have 6-8 colds/year

the common cold

What is the Etiology and Pathogenesis of the common cold

• Associated with a number of viruses. Examples:

  • Rhinoviruses (most common),

  • parainfluenza,

  • respiratory syncytial virus (RSV),

  • human metapneumovirus (hMPV),

  • coronaviruses,

  • adenoviruses,

  • bocaviruses (in children)

• Factors in identifying the type of virus:

  • Season

  • Age

    • RSV and parainfluenza: Children < 6 years old

    • Frequency of infections decreases with age until about 65 year

  • Immunological state

  • prior exposure

  
  

  • Common source of spread: FINGERS

  • Common portals of entry: eyes and nasal mucosa

  • incubation period = 2 days

  • Duration of illness = 7 days

• Viral shedding usually peaks around the time of illness then declines. May be present for a few weeks.

What is the common source of spread for the common cold, and common portals of entry?

• Common source of spread: FINGERS

• Common portals of entry: eyes and nasal mucosa

incubation and duration of the common cold

• incubation period = 2 days

• Duration of illness = 7 days

Manefestations of the common cold

• Dryness/stuffiness affecting mainly the nasopharynx

• Rhinitis

• Secretions are usually clear and watery

• Red, swollen mucous membranes of upper respiratory tract

• Postnasal dripping leading to sore throat and hoarseness

• Possible headache and generalized malaise

• Severe cases: chills, fever, and exhaustion

What is being described:

• Inflammation involving the nasal sinuses.

• Sinuses should remain sterile, but their lower oxygen content and warm/moist
  environment could facilitate the growth of organisms

• Most common causes are conditions that obstruct drainage from the sinuse

  • Swelling from viral upper respiratory tract infection or allergic rhinitis

  • Nasal polyps

  • Barotrauma from frequent changes in barometric pressure

  • Swimming, diving, and abuse of nasal decongestants

• can be accute or chronic

Rhinosinusitis (Rhino = nasal / Sinus = sinuses / Itis = inflammation)

Whats being described

• Caused by viruses, bacteria or mixed

• May last up to 4 weeks

• Common infecting organisms:

  • Haemophilus influenzae

  • Streptococcus pneumoniae

• Viral acute rhinosinusitis: 5-7 days

• Bacterial: worsening symptoms for 5-7 days or beyond 10 days

Acute Rhinosinusitis (Rhino = nasal / Sinus = sinuses / Itis = inflammation)

Manefestations of Acute Rhinosinusitis (Rhino = nasal / Sinus = sinuses / Itis = inflammation)

• Facial pain

• Headache

• Purulent nasal discharge

• Decreased sense of smell

• Fever

What is being described:

• Usually bacterial or fungal in origin

• Duration = > 12 weeks
  

• Caused by anaerobic organisms alone or in combination with aerobic organisms:

  • Strep species

  • Staphylococcus aureus

  • Possible presence of biofilms from Pseudomonas aeruginosa in ear, nose, throat

Chronic Rhinosinusitis (Rhino = nasal / Sinus = sinuses / Itis = inflammation)

Manefestations of Chronic Rhinosinusitis (Rhino = nasal / Sinus = sinuses / Itis = inflammation)

• Sinus pressure with nasal congestion

• Dull, constant headache

• Symptoms may persist for years with varying severity

• Episodes of acute sinusitis

• Mucosal changes often irreversible

What is being described

• A leading cause of death in the US

• Infection rates highest among children and older adults

• Rates of serious illness/death highest among adults > 65

• Mode of transmission: Inhalation of droplet nuclei

• Incubation period: 1-4 days (average of 2 days)

• Person may be contagious on day 1, even before showing symptoms, and remain infectious for ~ 1 week after illness onset.

• Viral shedding: May last up to 3 weeks

• Type A, B, and C cause epidemics in humans

influenza

Influenza incubation period

• Incubation period: 1-4 days (average of 2 days)

influenza mode of transportation

Inhalation of droplet nuclei

In influnza

a Person may be contagious on day 1, even before showing symptoms, and remain infectious for ~ 1 week after illness onset.

true

viral shedding of influnenza lasts how long

May last up to 3 weeks

What is Influenza type A

▪ Can infect multiple species (including avian and mammal species)

▪ Two subtypes based on two surface glycoproteins: Hemagglutinin (HA) and Neuraminidase (NA).

▪ Can develop new HA and NA subtypes in which the population is not protected.

▪ Antigenic shift: Major genetic rearrangement in either antigen HA or NA, May lead to epidemic or pandemic

▪ Antigenic drift: Lesser change in the virus; may allow partial protection for some individuals due to cross-reacting antibodies

What it a Major genetic rearrangement in either antigen HA or NA, May lead to epidemic or pandemic

influenza type A:

Antigenic shift

What is the Lesser change in the virus; may allow partial protection for some individuals due to cross-reacting antibodies

influenza type A:
Antigenic drift:

Pathogenesis of Influenza

• May cause three types of infections:

  • Uncomplicated upper respiratory infection (rhinotracheitis)

  • Viral pneumonia

  • Viral infection followed by a bacterial infection

• Initially an upper airway infection

  • Virus destroys mucous-secreting, ciliated, and epithelial cells

  • Holes between cells allow extra-cellular fluid to escape (“runny nose”)

• If virus moves lower in the respiratory tract…

  • Severe shedding of bronchial and alveolar cells

  • Compromised natural defense mechanisms

  • Bacteria easily adhere to epithelial cells → Secondary bacterial infection

Clinical manefestations of Influenza

• fever and chill

• Malaise

• muscle aching

• headache

• profuse, watery nasal discharge

• nonproductive cough

• sore cough

• possible diarrhea

Symptoms of uncomplicated rhinotracheitis usually peak on

day 3-5 and are gone by day 7-10