The onset of symptoms occurs 2 to 3 days after exposure to the infectious agent. The illness usually lasts for 7 to 10 days. Nasal congestion, sneezing and sore throat are the hallmarks of the common cold. The patients usually present with a runny nose, sneezing, post-nasal drip and throat pain. At first there is a clear mucus discharge from the nose. This often becomes thick and yellow or green within 2 to 3 days. The other symptoms include mild to high grade fever, conjunctivitis, fatigue and myalgias.

In some of the cases of upper respiratory infections, cough is the main symptom. This is because of the inflammation in the airways caused by infection. Cough is usually dry and associated with fever, headache and body aches.

In infants and children, the upper airways may become inflamed causing viral croup and acute laryngotracheobronchitis. Initially, the child gets a cold with cough, coryza and low grade fever. Gradually in 12 to 24 hours, the cough becomes croupy (also called “barking cough”). It causes varying degrees of respiratory distress with retractions and even cyanosis [7].

Upper respiratory tract infections are usually obvious from the common cold symptoms and do not require a medical diagnosis. However, the following investigations are necessary to establish the diagnosis with certainty.

• White blood cell count: Leukocytosis is very common with counts more than 10,000 per cubic millimeter and a predominance of polymorphs and immature neutrophils.
• Direct visualization: A laryngoscope helps visualize an enlarged, swollen and erythematous epiglottis in case of epiglottitis.
• Radiographic studies: X-ray of soft tissues of neck reveals subglottic narrowing. The presence of “thumb sign” is a common radiographic marker for epiglottitis [8].
• Throat culture: It is the primary method for the diagnosis of streptococcal pharyngitis and tonsillitis and the most reliable means of differentiating streptococcal from viral pharyngitis. Viral culture from nasopharyngeal secretions and viral antibody titer may help establishing the diagnosis of bronchiolitis.

In cases of upper respiratory infections, management is mostly symptomatic. Infants with respiratory distress should be hospitalized. Heated and humidified air may improve symptoms. The following agents may also be helpful.

• Nasal decongestants: Topical nasal decongestant sprays such as pseudoephedrine may be helpful [9]. They should only be used for 2 to 3 days.
• Intranasal cromolyn sodium and ipratropium bromide: These are helpful in reducing the severity of common cold symptoms.
• Analgesics: These include acetaminophen, aspirin and ibuprofen. They may help to improve the symptom of sore throat. Aspirin should not be used in children with acute viral illnesses because of the risk of Reye syndrome.
• Antibiotics: Antibiotics are used if the upper respiratory tract infection has a bacterial etiology [10].
• Antihistamines: These drugs help improve the symptoms like sneezing and rhinorrhea. These should be used with caution in elderly patients as they can cause sedation and anticholinergic effects.
• Ribavirin: It is an antiviral agent that can be used for the treatment of severe bronchiolitis due to respiratory syncytial virus.
• Intravenous fluids: They help to prevent dehydration. Respiratory acidosis and electrolyte imbalance must be corrected as well.
• Avoid smoking: Smoke irritates the nose and the throat. Therefore, staying away from smoky environments is recommended.
• Prop up position: Raising the head of your bed slightly by placing a pillow under the mattress may help reduce cough at night.

Most of the people with upper respiratory infections recover within a week with proper medication and good hygiene. So overall, the prognosis is excellent.

Untreated cases may lead to severe complications like otitis media, bronchitis, pneumonia and meningitis [6]. Serious complications may result in significant morbidity and rare deaths.

A number of viruses are responsible for causing upper respiratory infections. The most common virus responsible for common cold is rhinovirus. Other viruses include the coronavirus, parainfluenza virus, adenovirus, enterovirus, cytomegalovirus, coxsakievirus and respiratory syncytial virus. Over 200 viruses have been known to cause symptoms of the common cold.

Some cases of acute pharyngitis may also be caused by bacteria, most commonly Streptococcus pyogenes [2]. Other bacterial causes include Streptococcus pneumoniae, Hemophilus influenzae, Corynebacterium diphtheriae, Bordetella pertussis and Bacillus anthracis [3].

Acute upper respiratory tract infection is the leading cause of illness and death of children under 5 years of age. It constitutes around 30 to 60% of patients in a hospital outpatient. 80% of the children have upper respiratory infections.

Children usually have 3 to 8 episodes of viral respiratory infections per year. Adults have approximately 2 to 4 colds per year whereas people older than 60 years have less than one cold annually.

Streptococcal bacteria causes 5 to 15% of all cases of pharyngitis. Moreover, the upper respiratory infections are most common in cold weather, with a peak incidence from late winter to early spring. These illnesses are the leading reasons for people missing work and school.

Acute upper respiratory infections occur by transmission of microorganisms by aerosol, droplet or hand-to-hand contact with infected secretions. The viral infection arises from direct microbial invasion with subsequent bacteremia. This results in marked edema and inflammation with polymorphs and fibrin deposition.

The microorganisms encounter several barriers such as the hair lining the nose, mucus coats and ciliated cells lining the respiratory tract.

Initially, the infection occurs in the nasopharynx. It then extends to the larynx and trachea, causing redness and swelling and ultimately narrowing of the lumen by the fibrinous exudate.

Sometimes, genetic variations may also be involved in determining which patients have more severe disease courses than others [4][5].

The upper respiratory infections are usually contagious so the spread can be prevented by covering mouth and nose while coughing, washing hands carefully and avoiding touching one’s eyes and nose. Sharing of cups and kitchen utensils is also not to be avoided.

Regular exercise may also have a beneficial role as it helps improve the immune system. There are currently vaccines available that can provide protection against certain respiratory tract infections.

Upper respiratory infections include infections of the nose, sinuses, pharynx and larynx. The common cold is the most well-known form. Other types of upper respiratory infections include rhinitis, sinusitis, pharyngitis, epiglottitis, laryngitis, laryngotracheitis and tracheitis. These infections are the most common acute illnesses and are usually characterized by mild fever, cough, fatigue, sneezing and nasal congestion [1] and range from simple common cold to severe life threatening illnesses such as epiglottitis.

The upper respiratory infections are the most common illnesses of respiratory tract. The patients usually have mild fever with sore throat, a runny nose, cough and fatigue. Children tend to get more upper respiratory tract infections than adults.

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