Upper Respiratory Tract Infection (URTI)

Introduction:

• URTIs involve irritation and swelling of the upper airways, including the
  • nose
  • sinuses
  • pharynx
  • larynx
  • large airways.
• They encompass various conditions such as the
  • common cold
  • acute bronchitis
  • influenza
  • respiratory distress syndromes.
• Defining URTIs can be challenging due to overlapping symptoms and similar causative agents.

Etiology:

• Most commonly caused by viruses, including
  • rhinovirus
  • influenza virus
  • adenovirus
  • enterovirus
  • respiratory syncytial virus.
• Bacterial causes, notably Streptococcus pyogenes, account for a smaller proportion of cases, particularly in sudden onset pharyngitis.

Risk Factors:

• Close contact with children: both daycares and schools increase the risk
• Medical disorder: People with asthma and allergic rhinitis
• Smoking
• Immunocompromised individuals including those with cystic fibrosis, HIV, use of corticosteroids, transplantation, and post-splenectomy
• Anatomical anomalies including facial dysmorphic changes or nasal polyposis

Pathophysiology:

• Involves direct invasion of upper airway mucosa by pathogens acquired through inhalation of infected droplets.
• Protective mechanisms like nasal hair, mucus, and ciliated cells aid in preventing pathogen attachment.
• Immunological cells in adenoids and tonsils play a role in pathogen defense.

Influenza:

• Incubation period:
  • 1 to 4 days
  • viral shedding may precede symptom onset.
• Transmission modes:
  • direct contact
  • indirect contact
  • droplets
  • aerosolization.
• Direct contact and droplet transmission are primary modes.

Common Cold:

• Pathogens:
  • rhinovirus
  • adenovirus
  • parainfluenza virus
  • respiratory syncytial virus
  • enterovirus
  • coronavirus.
• Duration of symptoms:
  • 7 to 10 days on average, with potential persistence up to 3 weeks.

Differentials

• Allergic Rhinitis:
  • Classical symptoms include sneezing, itching (nose, eyes, throat), rhinorrhea (runny nose), and nasal congestion.
  • Signs may include pale or bluish nasal mucosa, swollen nasal turbinates, and allergic shiners (dark circles under the eyes).
• Sinusitis:
  • Classical symptoms include facial pain or pressure, nasal congestion, nasal discharge (which may be discolored), and reduced sense of smell.
  • Signs may include tenderness over affected sinuses, swelling of the face, and purulent nasal discharge.
• Tracheobronchitis:
  • Classical symptoms include cough (often productive), sore throat, hoarseness, and wheezing.
  • Signs may include rhonchi (continuous low-pitched rattling sounds), coarse breath sounds, and occasionally, fever.
• Pneumonia:
  • Classical symptoms include cough (productive or dry), fever, shortness of breath, chest pain, and fatigue.
  • Signs may include crackles or rales (discontinuous, crackling sounds), decreased breath sounds, increased respiratory rate, and dullness to percussion.
• Atypical Pneumonia:
  • Classical symptoms include gradual onset of symptoms, non-productive cough, headache, fatigue, and myalgias.
  • Signs may include fine inspiratory crackles, diffuse infiltrates on chest X-ray, and extrapulmonary manifestations like skin rash.
• Pertussis (Whooping Cough):
  • Classical symptoms include paroxysmal cough (often followed by a whooping sound), post-tussive vomiting, and inspiratory whoop.
  • Signs may include cyanosis (bluish discoloration of the skin), exhaustion, and apnea in infants.
• Epiglottitis:
  • Classical symptoms include sudden onset of high fever, severe sore throat, difficulty swallowing, and muffled voice.
  • Signs may include drooling, stridor (high-pitched breathing sounds), and tripod positioning (leaning forward with hands on knees or other support).
• Streptococcal Pharyngitis/Tonsillitis:
  • Classical symptoms include sore throat (often severe), painful swallowing, fever, headache, and swollen lymph nodes (especially anterior cervical lymphadenopathy).
  • Signs may include tonsillar exudates (white or yellow pus on the tonsils), erythema of the pharynx, and swollen, tender anterior cervical lymph nodes.
• Infectious Mononucleosis:
  • Classical symptoms include severe fatigue, sore throat, fever, swollen lymph nodes (especially cervical), and enlarged spleen or liver.
  • Signs may include pharyngeal erythema, palatal petechiae, and a characteristic rash (maculopapular rash) that may develop after administration of antibiotics.

History and Physical:

• Symptoms include cough, sore throat, runny nose, nasal congestion, headache, low-grade fever, facial pressure, sneezing, malaise, and myalgias.
• Onset typically 1 to 3 days post-exposure, with duration of 7-10 days, possibly up to 3 weeks.

Evaluation:

• Diagnosis based on clinical presentation; diagnostic testing often unnecessary.
• Nasal aspirates and swabs preferred for testing; rapid strep swabs useful for ruling out bacterial pharyngitis.

Treatment/Management:

• Nasal decongestants
  • Cochrane review on nasal decongestants showed unclear benefits when used as monotherapy in the common cold for the symptom of nasal congestion (Source)
  • Topical and oral nasal decongestants like oxymetazoline and pseudoephedrine reduce nasal airway resistance.
• Antibiotics
  • Evidence does not support antibiotic use as it does not improve symptoms or shorten illness duration.
  • Dextromethorphan lacks convincing evidence for acute cough management.
• Vitamin C Supplementation:
  • Daily prophylactic use (≥0.2 grams) modestly decreases common cold symptoms’ duration and severity.
  • Therapeutic use after symptom onset shows less clear benefits in trials.
  • According to a Cochrane Review, vitamin C used as daily prophylaxis at doses of ≥0.2 grams had a “modest but consistent effect” on the duration and severity of common cold symptoms (8% and 13% decreases in duration for adults and children, respectively). (Source)
• Antiviral Treatment for Influenza:
  • Neuraminidase Inhibitors:
    • oseltamivir
    • zanamivir
    • peramivir
  • They inhibit the viral neuraminidase enzyme, preventing viral escape from host cells and reducing symptom duration when initiated early.
  • Recommendations for Treatment:
    • should be promptly initiated for
      • severe disease
      • hospitalization
      • high-risk individuals
    • should begin within 48 hours of the onset of illness (regardless of laboratory confirmation availability)
      • but in severe disease treatment may still be beneficial if given outside this timeframe
    • Duration of therapy typically lasts five days, but may be extended in severe cases.
    • Antiviral Resistance:
      • At-risk populations, such as immunocompromised individuals and young children, are susceptible to antiviral resistance mutations.
      • Factors contributing to resistance include suboptimal dosing and cross-transmission of resistant strains.

Prevention/reduce transmission

• Routine vaccination
• hand hygiene
• cough etiquette
• voluntary home isolation

Vaccination (see influenza vaccine)

Antiviral Prophylaxis

1. Role of Neuraminidase Inhibitors:
   • Neuraminidase inhibitors, such as oseltamivir and zanamivir, can significantly reduce the risk of symptomatic influenza when used for prophylaxis.
   • However, prophylaxis should not be considered a substitute for vaccination.
2. Limitations:
   • Chemoprophylaxis does not completely eliminate the risk of influenza, and susceptibility returns once prophylaxis is stopped.
   • Prolonged chemoprophylaxis may lead to the emergence of influenza viruses with reduced susceptibility to antiviral drugs.

Prognosis:

• Generally benign, but can impair quality of life for weeks; complications rare except with influenza.
• Influenza complications may include viral and bacterial pneumonia, sinusitis, otitis media, and exacerbation of preexisting conditions.