Acute Respiratory Infections

• Respiratory tract is outlined by a continuous layer of mucosal surfaces from the nasopharynx to the lungs
• Acute respiratory infections < 28 days
• Wide variety of aetiological agents have been identified

Various classification methods including:

• Aetiological classification:
• Important for taking therapeutic decisions
• Anatomic/Syndromic classification is mostly used:
• Upper: Above the cricoid cartilage
• Lower: Below the cricoid cartilage

• Large paediatric burden
• 3-8 episodes per year in urban pre-school children
• 240/thousand infants & 34/thousand adolescents
• Majority are self-limiting viral URTIs
• Up to 4 million annual deaths amongst under-five children in developing countries

• Demographic factors
• Age
• Sex
• Host factors
• Nutritional status
• Immunisation status
• Socio-economic factors
• Family income and size;
• Parental literacy;
• Housing
• Environmental factors
• Housing parameters and parental cigarette smoking
• Outdoor automobile/industrial pollutants
• Day care attendance
• Others
• Low birth weight
• Cardiopulmonary abnormalities
• Atopy/allergy
• Lack of exclusive breastfeeding

• Modes of transmission:
• Inhalation of pathogen-containing aerosols
• Direct contact + self-inoculation
• Haematogenous spread
• Involves disruption of normal airway defense mechanisms:
• Anatomical/Mechanical Barriers- Nasal hairs; Mucus; Airway humidification; Absorption of gases in upper airway; etc.
• Protective Reflex Mechanisms- Cough reflex; Sneezing; Closure of epiglottis during deglutition; Laryngeal / Bronchospasm etc.
• Immunological Defence Mechanisms
• Cell mediated:
• Major defence against viral infections
• Major defence against mycobacterial and fungal infections
• Humoral
• Prevent / Reduce severity of viral infections
• IgA particularly important against bacteria and their toxins

Acute URTIs

• Uncomplicated: Acute Nasopharyngitis
• Complicated:
• Bacterial Sinusitis
• Acute Otitis Media
• Acute Epiglottitis
• Acute Pharyngitis (Tonsilitis)
• Retropharyngeal Abscess
• Retrotonsillar Abscess

Acute LRIs

• Uncomplicated
• Croup
• Acute Tracheobronchitis
• Acute Bronchiolitis
• Pneumonia
• Complicated
• Pleural Effusion and Empyema
• Pneumothorax and Hydro- or Pyopneumothorax

• AKA Common cold, Coryza, Acute rhinitis
• Commonest clinical syndrome
• Usually viral and self-limiting
• 3-8 episodes/year in pre-school kids

Aetiology

• Rhinovirus-50%; Corona virus; RSV adenovirus etc.

Pathogenesis

• Droplet inhalation; hand contamination.

Clinical Features:

• 2-3 days incubation then Sore throat, Nasal obstruction & Rhinorrhea.
• Minimal systemic toxicity. Self-limiting (7-10 days)

Treatment

• Mainly symptomatic and supportive
•  PCM; Fluids; Feeds; Clearing nostrils; Home remedy
•  Advise mother- what to expect and when to come back- return in 2 days or earlier if sicker, difficulty in breathing or fast breathing

Complications

• Due to spread to contiguous parts
• 2o bacterial infection

Prevention

• Interrupt spread of dx-
•  Hand washing; Face masks; Virucidal handkerchiefs; Intranasal α-interferon; Monoclonal antibodies;

Differential diagnosis:

• Allergic rhinitis: prominent itching and sneezing, nasal eosinophilia
• Foreign body: unilateral foul smelling secretion, may be bloody.
• Catarrhal stage of pertussis, high index of suspicion
• Measles prodromal stage
• Nasal diphtheria: bloody nasal discharge
• Congenital syphillis
• Influenza: same symptoms but of greater severity

Acute Inflammatory Lesion of Primary Site in the Pharynx ± Tonsils

Aetiology

• Frequently bacterial
• Group A beta Hemolytic Streptococci; C. diphtheriae; Klebsiella; Proteus; Pseudomonas; Fusiformis; H. influenzae; Adeno & enteroviruses

Pathogenesis

• Incubation period of 2-5 days (GABHS) then fever, throat pain, dysphagia, abdominal symptoms
• Tonsillar exudates; Anterior cervical lymphadenopathy

Investigations

Important to identify GABHS pharyngitis

• Specific: Throat culture; Antigen agglutination; Fluorescent antibody tests
• FBC; Lat cervical x-ray;

Complications

Suppurative:

• Cervical adenitis; Bacterial sinusitis; Retropharyngeal, Retrotonsillar, Lateral pharyngeal abscesses; Acute epiglottitis; Otitis media; LRTIs

Non-suppurative:

• AGN; Acute Rheumatic fever; Rheumatic carditis; Upper airway obstruction; Myocarditis; Polyneuritis

Treatment

• Specific: Penicillins; Erythromycin/Azithromycin; Antidiphtheritic antitoxin; Cephalosporins
• Non-specific: Warm fluids; Lozenges; PCM

Acute form as a complication of nasopharyngitis

Chronic form (>28 days) may also be from allergic inflammation or ciliary dyskinesia.

Aetiology

• Streptococcus pneumoniae, H. influenzae, M. catarrhalis; Chronic sinusitis - Anaerobic agents, H. influenzae, Strep. viridans, Staphylococcus aureus

Pathogenesis

• Defective sinus mucociliary clearance; Altered mucus coat; Nose blowing & Blockage of ostiomeatal drainage in viral nasopharyngitis and rhinosinusitis →→ Bacterial sinusitis

Clinical Features

• Protracted ‘cold’
• Daytime cough > 10 days but < 4 weeks
• Malodorous breath, ± fever
• Facial swelling
• Tenderness over the sinus
• Mucopurulent discharge from the middle meatus

Investigations

• Imaging
• Microbiological

Complications

Orbital Complications:

• Pre-septal/periorbital
• Orbital cellulitis

Intracranial/Osseous Complications:

• Epidural abscess, subdural empyema, Meningitis
• Cavernous sinus thrombosis, Frontal bone osteomyelitis

Haematogenous complications

Treatment

• Sterilize infected sinuses
• Prevent chronic sinusitis
• Prevent intraorbital/intracranial complications
• Medical ± Surgical irrigation and drainage

Prevention

• Avoid contact associated spread of Rh coryza
• Chemoprophylaxis or immunization to prevent post-influenza bacterial sinusitis

Suppurative inflammation of the mucous membrane of the middle ear cleft of relatively sudden clinical onset

Supraglottic lesions:

• Epiglottitis
• Retropharyngeal abscess
• Retrotonsillar abscess

Subglottic lesions:

• Viral croup
• Membranous croup (Bacterial tracheitis)
• Spasmodic croup