Respiratory tract infection

Respiratory tract infection refers to any of a number of infectious diseases involving the respiratory tract. An infection of this type is normally further classified as an upper respiratory tract infection (URI or URTI) or a lower respiratory tract infection (LRI or LRTI). Lower respiratory infections, such as pneumonia, tend to be far more serious conditions than upper respiratory infections, such as the common cold.
Upper respiratory tract infection
Although some disagreement exists on the exact boundary between the upper and lower respiratory tracts, the upper respiratory tract is generally considered to be the airway above the glottis or vocal cords. This includes the nose, sinuses, pharynx, and larynx.
Typical infections of the upper respiratory tract include tonsillitis, pharyngitis, laryngitis, sinusitis, otitis media, certain types of influenza, and the common cold. Symptoms of URIs can include cough, sore throat, runny nose, nasal congestion, headache, low grade fever, facial pressure and sneezing.
Upper respiratory tract infections (URI or URTI) are illnesses caused by an acute infection which involves the upper respiratory tract including the nose, sinuses, pharynx or larynx. This commonly includes tonsillitis, pharyngitis, laryngitis, sinusitis, otitis media, and the common cold.

Classification
• Rhinitis - Inflammation of the nasal mucosa
• Rhinosinusitis or sinusitis - Inflammation of the nose and paranasal sinuses, including frontal, ethmoid, maxillary, and sphenoid
• Nasopharyngitis (rhinopharyngitis or the common cold) - Inflammation of the nares, pharynx, hypopharynx, uvula, and tonsils
• Pharyngitis - Inflammation of the pharynx, hypopharynx, uvula, and tonsils
• Epiglottitis (supraglottitis) - Inflammation of the superior portion of the larynx and supraglottic area
• Laryngitis - Inflammation of the larynx
• Laryngotracheitis - Inflammation of the larynx, trachea, and subglottic area
• Tracheitis - Inflammation of the trachea and subglottic area

Signs and symptoms
Acute upper respiratory tract infections include rhinitis, pharyngitis/tonsillitis and laryngitis often referred to as a common cold, and their complications: sinusitis, ear infection and sometimes bronchitis (though bronchi are generally classified as part of the lower respiratory tract.) Symptoms of URTIs commonly include cough, sore throat, runny nose, nasal congestion, headache, low grade fever, facial pressure and sneezing. Onset of symptoms usually begins 1–3 days after exposure. The illness usually lasts 7–10 days.
Group A beta hemolytic streptococcal pharyngitis/tonsillitis (strep throat) typically presents with a sudden onset of sore throat, pain with swallowing and fever. Strep throat does not usually cause runny nose, voice changes, or cough.
Pain and pressure of the ear caused by a middle ear infection (otitis media) and the reddening of the eye caused by viral conjunctivitis are often associated with upper respiratory infections.

Cause
Over 200 different viruses have been isolated in patients with URIs. The most common virus is called the rhinovirus. Other viruses include the coronavirus, parainfluenza virus, adenovirus, enterovirus, and respiratory syncytial virus.
Up to 15% of acute pharyngitis cases may be caused by bacteria, most commonly Streptococcus pyogenes a Group A streptococcus in Streptococcal pharyngitis ("Strep Throat"). Other bacterial causes are Streptococcus pneumoniae, Haemophilus influenzae, Corynebacterium diphtheriae, Bordetella pertussis, and Bacillus anthracis.

Treatment
Treatment depends on the underlying cause. There are currently no medications or herbal remedies that have been conclusively demonstrated to shorten the duration of the illness. Treatment comprises symptomatic support usually via analgesics for headache, sore throat and muscle aches.
Moderate exercise in sedentary subjects with naturally acquired URTI probably does not alter the overall severity and duration of the illness. Mild sleep deprivation has been shown to be associated with increased susceptibility to infection. No randomized trials have been conducted to ascertain benefits of increasing fluid intake.

Lower respiratory tract infection
The lower respiratory tract consists of the trachea (wind pipe), bronchial tubes, the bronchioles, and the lungs.
Lower respiratory tract infections are generally more serious than upper respiratory infections. LRIs are the leading cause of death among all infectious diseases. The two most common LRIs are bronchitis and pneumonia. Influenza affects both the upper and lower respiratory tracts, but more dangerous strains such as the highly pernicious H5N1 tend to bind to receptors deep in the lungs.

Lower respiratory tract infection (LRTI), while often used as a synonym for pneumonia, can also be applied to other types of infection including lung abscess and acute bronchitis. Symptoms include shortness of breath, weakness, fever, coughing and fatigue.
There are a number of infections that can affect the lower respiratory tract. The two most common are bronchitis and pneumonia.
Influenza affects both the upper and lower respiratory tracts.
Antibiotics are the first line treatment for pneumonia; however, are not indicated in viral infections. Acute bronchitis typically resolves on its own with time.
In 2013 LRTIs resulted in 2.7 million deaths down from 3.4 million deaths in 1990. This was 4.8% of all deaths in 2013.

Causes


Bronchitis
Bronchitis can be classified as either acute or chronic. Acute bronchitis can be defined as acute bacterial or viral infection of the larger airways in healthy patients with no history of recurrent disease. It affects over 40 adults per 1000 each year and consists of transient inflammation of the major bronchi and trachea. Most often it is caused by viral infection and hence antibiotic therapy is not indicated in immunocompetent individuals. There are no effective therapies for viral bronchitis. Treatment of acute bronchitis with antibiotics is common but controversial as their use has only moderate benefit weighted against potential side effects (nausea and vomiting), increased resistance, and cost of treatment in a self-limiting condition. Beta2 agonists are sometimes used to relieve the cough associated with acute bronchitis. In a recent systematic review it was found there was no evidence to support their use.
Acute Exacerbations of Chronic Bronchitis (AECB) are frequently due to non-infective causes along with viral ones. 50% of patients are colonised with Haemophilus influenzae, Streptococcus pneumoniae or Moraxella catarrhalis. Antibiotics have only been shown to be effective if all three of the following symptoms are present: increased dyspnoea, increased sputum volume and purulence. In these cases 500 mg of Amoxycillin orally, every 8 hours for 5 days or 100 mg doxycycline orally for 5 days should be used.

Pneumonia
Pneumonia occurs in a variety of situations and treatment must vary according to the situation. It is classified as either community or hospital acquired depending on where the patient contracted the infection. It is life-threatening in the elderly or those who are immunocompromised. The most common treatment is antibiotics and these vary in their adverse effects and their effectiveness. Pneumonia is also the leading cause of death in children less than five years of age. The most common cause of pneumonia is pneumococcal bacteria, Streptococcus pneumoniae accounts for 2/3 of bacteremic pneumonias. This is a dangerous type of lung infection with a mortality rate of around 25%. For optimal management of a pneumonia patient, the following must be assessed: pneumonia severity (including treatment location, e.g., home, hospital or intensive care), identification of causative organism, analgesia of chest pain, the need for supplemental oxygen, physiotherapy, hydration, bronchodilators and possible complications of emphysema or lung abscess.

Prevention
Vaccination help prevent LRTIs, mostly against influenza viruses, adenoviruses, measles, rubella, streptococcus pneumoniae, haemophilus influenzae, diphtheria, bacillus anthracis, and bordetella pertussis.