Upper Respiratory Tract Infection

Etiology

Common cold continues to be a large burden on society, economically and socially. The most common virus is rhinovirus. Other viruses include the influenza virus, adenovirus, enterovirus, and respiratory syncytial virus. Bacteria may cause roughly 15% of sudden onset pharyngitis presentations. The most common is S. pyogenes, a Group A streptococcus.

Risk factors for a URTI

• Close contact with children: both daycares and schools increase the risk fo URI
• Medical disorder: People with asthma and allergic rhinitis are more likely to develop URI
• Smoking is a common risk factor for URI
• Immunocompromised individuals including those with cystic fibrosis, HIV, use of corticosteroids, transplantation, and post-splenectomy are at high risk for URI
• Anatomical anomalies including facial dysmorphic changes or nasal polyposis also increase the risk of URI

Epidemiology

Across the country, URIs are one of the top three diagnoses in the outpatient setting.   Estimated annual costs for viral URI, not related to influenza, exceeds $22 billion. [2] Upper respiratory tract infections account for an estimated 10 million outpatient appointments a year. Relief of symptoms is the main reason for outpatient visits amongst adults during the initial couple weeks of sickness, and a majority of these appointments result with physicians needless writing of antibiotic prescriptions. Adults obtain a common cold around two to three times yearly whereas pediatrics can have up to eight cases yearly.[3],[4],[5]  Fall months see a peak in incidence of common cold caused by the rhinovirus. Upper respiratory tract infections are accountable for greater than 20 million missed days of school and greater than 20 million days of work lost, thus generating a large economic burden. [6]

Pathophysiology

A URTI usually involves direct invasion of the upper airway mucosa by the organism. The organism is usually acquired by inhalation of infected droplets. Barriers that prevent the organism from attaching to the mucosa include 1) the hair lining that traps pathogens, 2) the mucus which also traps organisms 3) the angle between the pharynx and nose which prevents particles from falling into the airways and 4) ciliated cells in the lower airways that transport the pathogens back to the pharynx.

The adenoids and tonsils also contain immunological cells that attack the pathogens.

Influenza

The incubation period for influenza is 1 to 4 days, and the time interval between symptom onset is estimated to be 3 to 4 days. Viral shedding can occur 1 day before the onset of symptoms. It is believed that influenza can be transferred among humans by direct contact, indirect contact, droplets, or aerosolization. Short distances (<1 meter) are generally required for contact and droplet transmission to occur between the source person and the susceptible individual. Airborne transmission may occur over longer distances (>1 m). Most evidence-based data suggest that direct contact and droplet transfer are the predominant modes of transmission for influenza. [7]

Common Cold

The pathogens are responsible for causing the common cold include rhinovirus, adenovirus, parainfluenza virus, respiratory syncytial virus, enterovirus, and coronavirus. The rhinovirus, a species of the Enterovirus genus of the Picornaviridae family, is the most common cause of the common cold and causes up to 80% of all respiratory infections during peak seasons.[8] Dozens of rhinovirus serotypes and frequent antigenic changes among them make identification, characterization, and eradication complex. After deposition in the anterior nasal mucosa, rhinovirus replication and infection are thought to begin upon mucociliary transport to the posterior nasopharynx and adenoids. As soon as 10 to 12 hours after inoculation, symptoms may begin. The mean duration of symptoms is 7 to 10 days, but symptoms can persist for as long as 3 weeks. Nasal mucosal infection and the host's subsequent inflammatory response cause vasodilation and increased vascular permeability. These events result in nasal obstruction and rhinorrhea whereas cholinergic stimulation prompts mucus production and sneezing.

History and Physical

Acute upper respiratory tract infections include rhinitis, pharyngitis, tonsillitis, and laryngitis. Symptoms of URTIs commonly include:

• Cough
• Sore throat
• Runny nose
• Nasal congestion
• Headache
• Low-grade fever
• Facial pressure
• Sneezing
• Malaise
• Myalgias

The onset of symptoms usually begins one to three days after exposure and lasts 7–10 days, and can persist up to 3 weeks.

Evaluation

The presence of classical features for rhinovirus infection, coupled with the absence of signs of bacterial infection or serious respiratory illness, is sufficient to make the diagnosis of the common cold. The common cold is a clinical diagnosis, and diagnostic testing is not necessary. When testing for influenza, obtain specimens as close to symptom onset as possible. Nasal aspirates and swabs are the best specimens to obtain when testing infants and young children. For older children and adults, swabs and aspirates from the nasopharynx are preferred. Rapid strep swabs can be used to rule out bacterial pharyngitis, which could help decrease number of antibiotics being prescribed for these infections.

Treatment / Management

The goal of treatment for the common cold is symptom relief. Decongestants and combination antihistamine/decongestant medications can limit cough, congestion, and other symptoms in adults.[9] Avoid cough preparations in children.[10] H1-receptor antagonists may offer a modest reduction of rhinorrhea and sneezing during the first 2 days of a cold in adults. [3] First-generation antihistamines are sedating, so advise the patient about caution during their use. Topical and oral nasal decongestants (i.e., topical oxymetazoline, oral pseudoephedrine) have moderate benefit in adults and adolescents in reducing nasal airway resistance.[10], [3] Evidence-based data does not support the use of antibiotics in the treatment of the common cold because they do not improve symptoms or shorten the course of illness.[10], [3] There is also a lack of convincing evidence supporting the use of dextromethorphan for acute cough.(A1)

According to a Cochrane Review,[11] vitamin C used as daily prophylaxis at doses of =0.2 grams or more had a "modest but consistent effect" on the duration and severity of common cold symptoms (8% and 13% decreases in duration for adults and children, respectively). When taken therapeutically after the onset of symptoms, however, high-dose vitamin C has not shown clear benefit in trials.[11](A1)

Early antiviral treatment for influenza infection shortens the duration of influenza symptoms, decreases the length of hospital stays, and reduces the risk of complications.[ Recommendations for the treatment of influenza are updated frequently by the Centers for Disease Control and Prevention based on epidemiologic data and antiviral resistance patterns. Give antiviral therapy for influenza within 48 hours of symptom onset (or earlier), and do not delay treatment for laboratory confirmation if a rapid test is not available. Antiviral treatment can provide benefit even after 48 hours in pregnant and other high-risk patients.[12]

Vaccination is the most effective method of preventing influenza illness. Antiviral chemoprophylaxis is also helpful in preventing influenza (70% to 90% effective) and should be considered as an adjunct to vaccination in certain scenarios or when vaccination is unavailable or not possible. Generally, antiviral chemoprophylaxis is used during periods of influenza activity for (1) high-risk persons who cannot receive vaccination (due to contraindications) or in whom recent vaccination does not, or is not expected to, afford a sufficient immune response; (2) controlling outbreaks among high-risk persons in institutional settings; and (3) high-risk persons with influenza exposures. [13](A1)

Differential Diagnosis

• Common Cold
• Allergic rhinitis
• Sinusitis
• Tracheobronchitis
• Pneumonia
• Influenza
• Atypical Pneumonia
• Pertussis
• Epiglottitis
• Streptococcal Pharyngitis/Tonsillitis
• Infectious Mononucleosis

Prognosis

URI are common during the winter season and for the most part, are benign, but they can seriously affect the quality of life for a few weeks. A few individuals may develop pneumonia, meningitis, sepsis, and bronchitis. Each year, there are isolated cases of death reported from a URI. Time off work and school is very common. In addition, patients spend billions of dollars on worthless remedies. There is little evidence that any treatment actually shortens the duration of a viral URI. Even the vaccine only works in 40-60% of individuals, at best.

Complications

Complications of upper respiratory tract infections are relatively rare, except with influenza. Complications of influenza infection include primary influenza viral pneumonia; secondary bacterial pneumonia; sinusitis; otitis media; coinfection with bacterial agents; and exacerbation of preexisting medical conditions, particularly asthma and chronic obstructive pulmonary disease. Pneumonia is one of the most common complications of influenza illness in children and contributes significantly to morbidity and mortality.