INFECTION OF THE RESPIRATORY TRACT

• Infections involving the respiratory tract are classified as upper respiratory tract infections and lower respiratory tract infections

  
• The upper respiratory tract is from the nose down to the larynx including the sinuses while the lower respiratory tract includes the bronchial tree and the lungs

  
• Respiratory tract infections may be caused by a myriad of organisms—viruses, bacteria and fungi

  
• Risk factors that promote the development of respiratory tract infections


  • The most critical factor is the quality or condition in the environment
  • Most preventable infections can be attributed to poor environmental standards such as poor housing conditions, overcrowding, and air pollution both inside and outside the home

  
• Respiratory tract infections are transmitted

  1. By person to person which may involve direct spread via droplet nuclei (e.g., sneezing, talking, or coughing resulting in discharge of airborne particles from the respiratory tract of the infected person)

  2. Through indirect spread via articles or hands contaminated with the person's infectious secretions

  
• Common Cold (acute rhinitis)


  A common illness in both children and adults
• The incidence and seasonal occurrence of the common cold tend to be predictable
• The common cold commonly occurs in school settings, especially with the proliferation of day care centers
• Transmission of colds


  Close personal contact is necessary
• Source of infection for the common cold

  The greatest concentration of the etiologic agent (most commonly due to rhinovirus) is in the nasal secretions and the greatest source of infection is through sneezing, nose blowing, and contamination of external surfaces with nasal secretions

  
• Manifestations of the common cold

  • Fever (in older children)
  • Sneezing with breathing watery nasal discharge (runny nose or rhinorrhea/coryza)
  • Nasal congestion
  • Nasal secretions becoming thicker and purulent after 1-3 days
• Viruses remain to be the most common etiologic agents of the common cold
• Infectious agents associated with the common cold

  • Rhinovirus (most common)
  • Parainfluenza viruses
  • Respiratory syncytial virus
  • Coronavirus
  • Adenoviruses
  • Enteroviruses
  • Influenza viruses
  • Reoviruses
  • Mycoplasma pneumoniae
  • Coccidioides immitis
  • Histoplasma capsulatum
  • Bordetella pertussis
  • Chlamydia psittaci
  • Coxiella burnetti

  
• Antibiotics have no role in the management of the common cold
• Management of the common cold


  Mainly symptomatic, Paracetamol can be given for fever, the true efficacy of decongestants has not been determined yet
• Rhinoviruses


  The main cause of the common cold, non enveloped RNA viruses that have more than 100 serologic types, primarily affect the nose and conjunctiva, can withstand adverse environmental conditions and can survive the external environment for many hours but are killed by gastric acid when swallowed

  
• Coronaviruses


  The second most common cause of the common cold, enveloped RNA viruses, infection occurs worldwide and the virus is mainly transmitted by respiratory aerosol, in 2002 a new disease called SARS (Severe Acute Respiratory Syndrome) emerged and coronavirus was implicated as the etiologic agent, the civet cat was identified as the likely reservoir of CoV SARS

  
• SARS


  A severe form of atypical pneumonia characterized by fever, non productive cough, dyspnea, and hypoxia, chills, rigors, malaise, and headache commonly occur, the incubation period ranges from 2 to 10 days
• There is no antiviral therapy or vaccine available for SARS, there have been attempts of using a combination of ribavirin and steroids in the treatment of SARS but the efficacy is still undetermined
• Adenoviruses


  Non enveloped DNA viruses that cause a variety of upper and lower respiratory tract diseases such as pharyngitis, conjunctivitis, common cold, and pneumonia, they also cause keratoconjunctivitis, hemorrhagic cystitis, and gastroenteritis

  
• Modes of transmission for adenoviruses

  • Aerosol droplet – transmission of pathogens through the air
  • Fecal oral – most common mode of transmission among young children and their families
  • Direct inoculation of conjunctiva by fingers – transmission may occur when coming into contact with contaminated surfaces

  
• Clinical findings of adenovirus infections

  • Upper respiratory tract infections:
  • Nasopharyngitis – characterized by the swelling of the nasal passages and the back of the throat
  • Pharyngoconjunctival fever – acute respiratory disease characterized by fever, sore throat, coryza (runny nose), and conjunctivitis
  • Lower respiratory tract infections:
  • Bronchitis – inflammation of the brocial tubes
  • Atypical pneumonia – infection caused by different bacteria than the common ones that cause pneumonia
  • Hemorrhagic cystitis – characterized by hematuria and dysuria
  • Gastroenteritis – with non bloody diarrhea in children younger than 2 years of age

  
• There is no antiviral therapy, live, non attenuated adenovirus vaccine for serotypes 4, 7, and 21 has been developed but was used only by the military and is no longer used now
• Pharyngitis


  Inflammation of the mucous membranes of the pharynx, the clinical diagnostic category includes tonsillitis, tonsillopharyngitis, and nasopharyngitis
• Nasopharyngitis


  A common illness of childhood, occurring more commonly during the cold weather months, the most common causes are adenoviruses, frequently causing infection in adolescent and young adults in military training, other viruses that can also cause the disease are influenza and parainfluenza viruses, it is an acute, self limited disease lasting 4 to 10 days
• Diagnosis of nasopharyngitis is based on clinical manifestations, management is mainly supportive, the use of throat lozenges, aseptic mouthwash, and decongestants have no role in the management of the infection
• Tonsillopharyngitis


  Inflammation involving both the pharynx and the tonsils, has a seasonal occurrence and usually involves children 5-10 years of age, with a secondary peak at 12 and 18-20 years of age, the most common cause is Streptococcus pyogenes, it is obtained primarily by direct contact with large droplets or respiratory secretions

  
• Manifestations of tonsillopharyngitis


  • Sudden onset of fever, sore throat, headache, nausea, malaise, and pain
  • Marked tonsillo pharyngeal erythema
• Diagnosis of tonsillopharyngitis


  The gold standard is culture of specimen obtained by swab of the posterior pharyngeal and tonsillar regions
• Complications of tonsillopharyngitis


  Sinusitis, otitis media, peritonsillar and retropharyngeal abscess, acute rheumatic fever, and acute glomerulonephritis
• Treatment of tonsillopharyngitis


  Antibiotic treatment is necessary, the drug of choice is penicillin, erythromycin or clindamycin may be given as an alternative for patients allergic to penicillin

  
• Scarlet Fever


  Infection that occurs in association with streptococcal pharyngitis and is caused by Streptococcus pyogenes strains producing streptococcal pyrogenic exotoxin or formerly known as erythrogenic toxin, the toxin causes a hypersensitivity reaction producing a pinkish red rash on the skin
• Treatment of Scarlet Fever


  The drug of choice is penicillin G, control measures are directed mainly at the human source as the disease is transmitted primarily by inhalation of infective droplets from an infected person
• Sinusitis


  Inflammation of the mucosal lining of one or more of the paranasal sinuses, common in children with allergies, or adenoids and enlarged tonsils, dental infections, and in children with chronic ear infections, the principal pathogens are Haemophilus influenzae and Streptococcus pneumoniae
• Clinical features of sinusitis

  • In young children: persistent rhinorrhea (nasal discharge) with a daytime cough that is worse at night, periorbital edema, post nasal drip, and foul smelling breath
  • In older children or adults: headaches, dental and facial pain with tenderness over the involved sinuses on palpation
• Diagnosis of sinusitis


  Specific diagnosis involves culture with specimen taken from the infected sinus, X-ray may also be done to demonstrate the involved sinus
• Treatment of sinusitis


  Antimicrobial therapy is done to achieve clinical improvement and sterilization of sinus secretions, it is given for 7 days or more, other measures include: normal saline washes to liquefy secretions and enhance mucociliary transport, use of anti histamines if allergic rhinitis is contributory, corticosteroids to reduce inflammation but must be used with caution because of risk of superinfection, and surgical drainage
• Otitis Externa


  Inflammation involving the external ear, the more common cause in tropical countries is Pseudomonas aeruginosa, other causes are Staphylococcus aureus, Proteus vulgaris, Klebsiella, and Escherichia coli, itching and pain are prominent and intense pain is felt when the tragus is pulled, periaural edema and complete obliteration of the canal may be seen in severe infection
• Diagnosis and management of otitis externa

  Diagnosis is made based on clinical presentation, management includes flushing or irrigation of the external auditory canal with 3% hypertonic saline, if there is no evidence of infection, use of topical corticosteroid cream is sufficient, in the presence of overt infection, Neosporin cream must be applied three times a day, preventive measures include minimizing swimming and exposure to water and minimizing excessive cleaning of the ears
• Otitis Media


  Inflammation of the mucoperiosteallining of the middle ear, two thirds of cases are caused by bacteria with Streptococcus pneumoniae as the most common and Haemophilus influenzae as the second most common cause, viral causes include respiratory syncytial virus, influenza virus, adenovirus, and rhinovirus