Respiratory tract infections

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Respiratory tract infections:

Upper respiratory tract infections:
Common cold/acute coryza:
• to due 100+ strains of rhinoviruses; 1-4 day incubation
• rapid onset; burning sensation in nose; sore throat; sneezing; blocked nose; watery discharge
• treatment not usually needed as self limiting; symptomatic relief with paracetamol; nasal decongestants

Influenza:
• caused by three subtypes of the RNA orthomyxovirus; mutations frequently occur  new antigenic properties from new strain (immunity is usually to only one strain) ; spread by droplets; incubation of 1-4 days; infective from 1 day prior to symptoms to 1 week after onset
• acute onset – pyrexia, general aches and pains (myalgias), headache, anorexia, nausea, vomiting, harsh unproductive cough
• usually subside in 3-5 days; can vary from mild to potentially fatal
• complications – tracheitis, bronchitis (20%), pneumonia, secondary bacterial infection, sinusitis, otitis media. Rare complications  toxic cardiomyopathy, encephalitis, encephalopathy, peripheral neuropathy
• management – bed rest, paracetamol/aspirin, specific treatment of complications

Pneumonia:
Acute infection of lower respiratory tract.

Classified as being community acquired (usually Strep. pneumoniae, Chlamydia pneumoniae, Mycoplasma pneumoniae, Legionella pneumoniae) or hospital acquired/nosocomial (usually gram-negative – Esherichia, Pseudomonas, Klebsiella), or those in an immunosuppressed host (often Pneumocystis carinii, Pseudomonas aeruginosa).

Clinical features:
Short history of cough, fever, malaise – often with pleuritic chest pain; cough is initially short and dry, later productive and rust coloured; malaise; anorexia; sweats; fever; chest x-ray abnormalities

Complications – empyema, pleural effusion, septicaemia, lobar collapse, thromboembolic disease, pneumothorax, lung abscess

Management:
Antibiotics
If hypoxaemic  oxygen

Lung abscess:
Area(s) of localised suppurative infection in lung.

Aetiology – poor treated pneumonia; aspiration; bronchial obstruction; septic emboli; spread from other site

Clinical features – fever, cough, haemoptysis, pleuritic chest pain, malaise, weight loss, nail clubbing, anaemia

Treatment – antibiotics; postural drainage

Pulmonary Tuberculosis:
Disease was under control in most countries, but now becoming a more serious problem due to AIDS.

Greatest risk in – children, immunocompromised (eg AIDS), healthcare workers, those living in overcrowded conditions, chronic diseases (eg diabetes mellitus, alcoholism).

Due to Mycobacterium tuberculosis, Myco. bovis, Myco. kansasii, Myco. xenopi, Myco. malmoense

Clinical features – persistent cough, haemoptysis, pleural pain, weight loss, lethargy, spontaneous pneumothorax

Complications – pleurisy, pneumothorax, empyema, tuberculosis enteritis, blood-borne dissemination, respiratory failure, right ventricular failure

Fungal infections:
Aspergillosis:
• usually due to A. funigatus.

Allergic bronchopulmonary aspergillosis:
• due to allergic reaction to A. funigatus.
• initially causes bronchoconstriction  later progresses to bronchiectasis
• skin prick test confirms hypersensitivity
• prednisone given for inflammation

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