A variety of viruses and bacteria can cause upper respiratory tract infections. These cause a variety of patient diseases including acute bronchitis, the common cold, influenza, and respiratory distress syndromes. Defining most of these patient diseases is difficult because the presentations connected with upper respiratory tract infections (URIs) commonly overlap and their causes are similar. Upper respiratory tract infections can be defined as: self-limited irritation and swelling of the upper airways with associated cough with no proof of pneumonia, lacking a separate condition to account for the patient symptoms, or with no history of COPD/emphysema/chronic bronchitis.  Upper respiratory tract infections involve the nose, sinuses, pharynx, larynx, and the large airways.
Common cold continues to be a large burden on society, economically and socially. The most common virus is the 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.
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.  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.,, 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. 
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. 
The pathogens 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. 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 mucocilliary 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.
Acute upper respiratory tract infections include rhinitis, pharyngitis, tonsillitis, and laryngitis. Symptoms of URTIs commonly include:
The onset of symptoms usually begins one to three days after exposure and lasts 7–10 days, and can persist up to 3 weeks.
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.
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. Avoid cough preparations in children. H1-receptor antagonists may offer a modest reduction of rhinorrhea and sneezing during the first 2 days of a cold in adults.  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.,  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.,  There is also a lack of convincing evidence supporting the use of dextromethorphan for acute cough.
According to a Cochrane Review, 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.
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.
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. 
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.
Upper respiratory tract infections are one of the most common illnesses that healthcare workers will encounter in an outpatient setting. The infection may vary from the common cold to a life-threatening illness like acute epiglottitis. Because of the diverse causes and presentation, upper respiratory tract infections are best managed by a multidisciplinary team. The key is to avoid over-prescribing of antibiotics but at the same time not missing a life-threatening infection. Nurse practitioners who see these patients should freely communicate with an infectious disease expert if there is any doubt about the severity of the infection. Similarly, the emergency department physician should not readily discharge patients home with antibiotics for the common cold. Overall, upper respiratory tract infections lead to very high disability for short periods. Absenteeism from work and schools is common; in addition, the symptoms can be annoying and extreme fatigue is the norm. Patients should be encouraged to drink ample fluids, rest, discontinue smoking and remain compliant with the prescribed medications.
|||Wenzel RP,Fowler AA 3rd, Clinical practice. Acute bronchitis. The New England journal of medicine. 2006 Nov 16 [PubMed PMID: 17108344]|
|||Fendrick AM,Monto AS,Nightengale B,Sarnes M, The economic burden of non-influenza-related viral respiratory tract infection in the United States. Archives of internal medicine. 2003 Feb 24 [PubMed PMID: 12588210]|
|||Arroll B, Common cold. BMJ clinical evidence. 2008 Jun 9 [PubMed PMID: 19450292]|
|||Winther B,Gwaltney JM Jr,Mygind N,Hendley JO, Viral-induced rhinitis. American journal of rhinology. 1998 Jan-Feb [PubMed PMID: 9513654]|
|||Simasek M,Blandino DA, Treatment of the common cold. American family physician. 2007 Feb 15 [PubMed PMID: 17323712]|
|||Adams PF,Hendershot GE,Marano MA, Current estimates from the National Health Interview Survey, 1996. Vital and health statistics. Series 10, Data from the National Health Survey. 1999 Oct [PubMed PMID: 15782448]|
|||Brankston G,Gitterman L,Hirji Z,Lemieux C,Gardam M, Transmission of influenza A in human beings. The Lancet. Infectious diseases. 2007 Apr [PubMed PMID: 17376383]|
|||Heikkinen T,J�rvinen A, The common cold. Lancet (London, England). 2003 Jan 4 [PubMed PMID: 12517470]|
|||Irwin RS,Baumann MH,Bolser DC,Boulet LP,Braman SS,Brightling CE,Brown KK,Canning BJ,Chang AB,Dicpinigaitis PV,Eccles R,Glomb WB,Goldstein LB,Graham LM,Hargreave FE,Kvale PA,Lewis SZ,McCool FD,McCrory DC,Prakash UBS,Pratter MR,Rosen MJ,Schulman E,Shannon JJ,Hammond CS,Tarlo SM, Diagnosis and management of cough executive summary: ACCP evidence-based clinical practice guidelines. Chest. 2006 Jan [PubMed PMID: 16428686]|
|||Fashner J,Ericson K,Werner S, Treatment of the common cold in children and adults. American family physician. 2012 Jul 15 [PubMed PMID: 22962927]|
|||Douglas RM,Hemil� H,Chalker E,Treacy B, Vitamin C for preventing and treating the common cold. The Cochrane database of systematic reviews. 2007 Jul 18 [PubMed PMID: 17636648]|
|||Siston AM,Rasmussen SA,Honein MA,Fry AM,Seib K,Callaghan WM,Louie J,Doyle TJ,Crockett M,Lynfield R,Moore Z,Wiedeman C,Anand M,Tabony L,Nielsen CF,Waller K,Page S,Thompson JM,Avery C,Springs CB,Jones T,Williams JL,Newsome K,Finelli L,Jamieson DJ, Pandemic 2009 influenza A(H1N1) virus illness among pregnant women in the United States. JAMA. 2010 Apr 21 [PubMed PMID: 20407061]|
|||Harper SA,Bradley JS,Englund JA,File TM,Gravenstein S,Hayden FG,McGeer AJ,Neuzil KM,Pavia AT,Tapper ML,Uyeki TM,Zimmerman RK, Seasonal influenza in adults and children--diagnosis, treatment, chemoprophylaxis, and institutional outbreak management: clinical practice guidelines of the Infectious Diseases Society of America. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2009 Apr 15 [PubMed PMID: 19281331]|
|||Le Maréchal M,Tebano G,Monnier AA,Adriaenssens N,Gyssens IC,Huttner B,Milanic R,Schouten J,Stanic Benic M,Versporten A,Vlahovic-Palcevski V,Zanichelli V,Hulscher ME,Pulcini C, Quality indicators assessing antibiotic use in the outpatient setting: a systematic review followed by an international multidisciplinary consensus procedure. The Journal of antimicrobial chemotherapy. 2018 Jun 1 [PubMed PMID: 29878218]|