Acute Upper Respiratory Infections

Acute Upper Respiratory Tract InfectionsAcute Upper Respiratory Tract Infections

Acute Upper Respiratory Infections


Acute Upper Respiratory tract infections are the most common infections worldwide. They range from mild forms of disease to severe and life-threatening conditions, such as epiglottitis.

Acute upper respiratory tract infections are classified according to their location into rhinosinusitis, sinusitis, rhinitis, rhinopharyngitis, pharyngitis, laryngitis, epiglottitis, and laryngotracheitis.

Diagnosis of acute respiratory tract infections usually based on clinical presentation and physical examination. For special cases, diagnostic workup is made, including etiological studies like viral PCR.


The most prevalent infections in the general population are upper respiratory tract infections. They have significant social repercussions because they are the main reason people miss work or school. They range from minor, self-limiting conditions like the common cold to catastrophic, potentially fatal conditions like epiglottitis.

Acute upper respiratory tract infections (AURTIs) comprise short-term mild to full-blown viral or bacterial infections like:

  • Sinusitis,
  • Pharyngitis,
  • Laryngitis,
  • and the Common cold,

Which are associated with a greater prevalence and economic costs. These infections, although minor, can ultimately lead to complications like pneumonia, which is the leading cause of death in the developing world. The majority of AURTIs, which affect essentially the entire upper respiratory system as well as connected structures like the middle ear and paranasal sinuses, are caused by viruses. (1)

Relevant Anatomy

The nose, nasal cavity, pharynx, and larynx, make up the upper respiratory system. Under normal conditions, air makes entrance through the nasal cavity through the nostrils, where it is warmed, humidified, and filtered before entering the respiratory system. After conditioning, the air makes its way to the lower respiratory system after passing through the pharynx, larynx, and trachea. Any upper respiratory tract disorder or infection may significantly alter the quality of air that is inhaled and the normal process of air conditioning, which may further affect how well the tracheobronchial tree and lung function. (2)

General Overview

These infections are generally mild in symptoms and typically self-limiting and manageable at home. Analgesics, anticholinergic drugs, antihistamines, antipyretics, antitussives, adrenergic agonists, corticosteroids, and decongestants are commonly used as symptomatic therapy; in severe rare cases, antibiotics are prescribed. Surgery is only occasionally necessary, and the most serious cases require care in an intensive care unit (ICU).

AURTI complications can include retropharyngeal abscess or cellulitis, bronchopneumonia, sepsis, toxic shock, adult respiratory distress syndrome (ARDS), post-extubation subglottic stenosis, and anoxic encephalopathy. AURTIs may also exacerbate or trigger bronchial hyperreactivity. (3)

Definitions of Upper Respiratory Tract Infections

Common upper respiratory infections Definition
Rhinosinusitis or sinusitis Inflammation of the nares and paranasal sinuses, including frontal, ethmoid, maxillary, and sphenoid sinuses.
Rhinitis Inflammation of the nasal mucosa.
Nasopharyngitis, Rhinopharyngitis (Common cold) Inflammation of the nares and pharynx.
Pharyngitis Inflammation of the pharynx, hypopharynx, uvula, and tonsils.
Epiglottitis Inflammation of the superior portion of the larynx and supraglottic area.
Laryngotracheitis Inflammation of the larynx, trachea, and subglottic area.
Laryngitis Inflammation of the larynx.

The majority of upper respiratory tract infections are due to bacteria and viruses that overcome the mucosal defenses. Most often, the infection being contagious spreads from person to person by direct contact with secretions or through breathing, as the respiratory droplets of the infected person remain in the air. Upper respiratory tract infections may have bacterial infections as a primary cause, but they may also result from the superinfection of an infection that is largely viral.

Risk Factors for Acute Upper Respiratory Infections

  • Close contacts, such as that between young children who attend kindergarten or school;
  • Traveling with exposure to many people;
  • Smoking (second-hand smoke);
  • Smog;
  • Alteration of mucosal resistance;
  • Anatomic alterations in the respiratory tract;
  • Nasal polyposis. (4)

Natural Lines of Defense

The respiratory system has an excellent defense against all types of pathogens. Physical, mechanical, humoral, and cellular immune responses are some of the protective mechanisms. A particularly effective mechanical barrier is the hair in the nose, which filters and traps certain viruses as well as mucus coatings. All sorts of particles are transported by ciliated epithelial cells that elevate the trapped air debris up to the pharynx, where they are then ingested by the stomach or alternatively can be spit.

  • When the pathogen has breached the physical barriers, humoral immunity works to lessen the local infections through cellular immunity as well as locally released immunoglobulin A and other immunoglobulins. (5)
  • To engulf and eliminate intruders, immunological and inflammatory cells (macrophages, monocytes, neutrophils, and eosinophils) work in concert using a variety of cytokines and other media. There is a higher chance of getting an upper respiratory infection or having a longer illness course if there is impaired immune function (inherited or acquired).
  • It is advised to pay extra care to those who have compromised immune systems, such as those with resected spleen, HIV infected individuals, cancer patients, patients on chemotherapy or dialysis, or are undergoing stem cell or organ transplantation. Because a simple upper respiratory tract infection can quickly turn into a systemic disease in immunocompromised individuals, adequate antibiotic therapy and follow-up care should be encouraged.

Identifying the Pathogen

Viral testing is typically not necessary, except in rare circumstances like suspected influenza or in patients with compromised immune systems. This is because the majority of upper respiratory tract infections are caused by viruses, and there are currently no effective targeted treatments for most viruses. Conjunctivitis is a very common finding in viral illness. Viral infections are also mostly self-limiting, resolving in about 7–10 days.

In some circumstances, it is necessary to look for the specific bacterial infection that is causing the condition. The most common bacterial infection is Streptococcal pharyngitis, sometimes referred to as “strep throat.” The common presentation of symptoms for Streptococcal pharyngitis are:

  • Fever (38.3°C for 24 hours);
  • Erythema;
  • Swelling or exudates on tonsils or pharynx;
  • Tender anterior cervical lymph nodes;
  • Absence of cough;
  • Rhinorrhea;
  • Occurrence during winter or allergy season. (6)

Modified Centor’s Criteria

For the purpose of clinical decision-making and risk stratification for group A Streptococccus (GAS) pharyngitis, the Modified Centor’s Criteria is used, which is a four-point scoring system. Each criterion is worth one point, and when the total number of points rises, the risk of GAS pharyngitis rises as well.

Individuals that meet a Centor’s score of 3 are typically tested for GAS; nevertheless, these patients are unlikely to develop GAS pharyngitis and typically do not require GAS testing. It should be kept in mind that these criteria do not replace testing for GAS and should not be used to evaluate whether or not antibiotic therapy is necessary because they are neither sensitive nor specific for the diagnosis of streptococcal pharyngitis. (7)

Modified Centor's Criteria ScoreGAS Infection Risk (%)AAP/IDSACDC/ACP/AAFP
01-2.5No test/treatmentNo test/treatment
15-10No test/treatmentNo test/treatment
211-17Rapid Antigen TestRapid Antigen Test
328-35Rapid Antigen TestTest or Treat Empirically
51-53Rapid Antigen TestTest or Treat Empirically

No more testing is required if clinical suspicion is strong, and treatment with an empiric antibiotic is directed. Further testing is advised when the diagnosis is uncertain.

The group A Streptococcus antigen test is efficient since it provides faster results in about 30 minutes and with an acceptable test specificity. For the usual primary assessment of adults with pharyngitis or for the verification of negative quick antigen testing, throat cultures are not advised. (8)

Diagnostic Testing in Upper Respiratory Infections

Sinus radiography is the radiological investigation of the facial bones and paranasal sinuses. In cases of trauma, postoperative evaluations, and dental radiography, plain radiography of the facial bones is still frequently employed. Plain radiography plays a very small part in sinusitis management. Although complete opacification of a sinus and air-fluid levels are more indicative of sinusitis, they are only present in 60% of instances. Computed Tomography (CT) scans without contrast allow for a significantly more detailed definition of the nasal anatomy. In 40% of symptomatic individuals, mucosal thickness, polyps, and other sinus abnormalities might be observed. But a strong clinical correlation is required to prevent overdiagnosis of sinusitis due to nonspecific CT findings. (9)

Although it cannot tell the difference between acute and chronic paranasal sinusitis, CT scanning can be useful in the diagnosis of acute and chronic sinusitis. The CT scan results must be interpreted in light of the clinical characteristics. Numerous non-specific CT findings may be found, such as diffusely thickened sinus mucosa.

The detection of sinonasal disease definitely involves nasal endoscopy, but it only applies to patients with severe symptoms, with a protracted course, or when there is a suspicion of serious complications.

When epiglottitis is suspected, laryngoscopy is carried out very cautiously and only in well-equipped medical facilities where any complications may be avoided. The equipment has the potential to cause respiratory damage, insufficiency, and airway spasms. (10)

AURTI CT Findings
Acute sinusitis


Air-fluid levels, sinus opacification, and thickened localized mucosa.
Chronic sinusitis


Mucosal thickening, opaque air cells, bony remodeling, and bony thickening, brought on by inflammatory osteitis of the sinus canal walls.

Rhinitis and Rhinosinusitis

A runny nose, rhinorrhea, sneezing, congestion, blockage of nasal breathing, and in certain cases, pruritus are all symptoms of rhinitis, an inflammation and swelling of the mucous membranes of the nose. Rhinitis can be either acute or chronic depending on the course of symptoms and the nasal mucosa changes. Infectious rhinitis is one of several reasons that make up the etiology of the condition. The propensity to cause obstructions in the intranasal passageways can lead to any kind of rhinitis resulting in an episode of sinusitis in an individual who is prone to it. (11)

Type of rhinitis Etiology


Infectious rhinitis Viruses, bacteria, fungi


Vasomotor rhinitis Disbalance of the parasympathetic and

sympathetic system


Occupational rhinitis



Inhaled irritants


Hormonal rhinitis Estrogen imbalance



ACEI, b-blockers, methyldopa, aspirin,

NSAID, phentolamine, chlorpromazine,

Estrogen, oral contraceptives


Gustatory rhinitis Hot and spicy food


Allergic rhinitis Various allergens


Nonallergic rhinitis (eosinophilia positive)



Abnormal prostaglandin metabolism


Viral Rhinosinusitis

Runny nose, sneezing, congestion, clear to mucopurulent nasal discharge, altered sense of smell, postnasal drip with cough, and low-grade fever are common symptoms of viral rhinosinusitis. There may also be pressure and soreness in the face, myalgia, weariness, rash associated with group A streptococcal infections or enterovirus, headache, and stomach problems. Symptomatic care, including analgesics, antipyretics, increased fluid intake, adequate rest, and saline irrigation, can assist in early recovery.

The majority of common colds are due to human rhinovirus, with the remainder coming from coronavirus, adenovirus, parainfluenza, respiratory syncytial virus, or enterovirus. Viral infections are also mostly self-limiting, resolving in about 7–10 days. (12)

Bacterial Rhinosinusitis

Mainly purulent (yellow-green) discharge, a moderate-to-high grade fever, and persistent acute rhinosinusitis symptoms lasting for about 10 days or an increase in symptom severity after 5-7 days are characteristic of bacterial rhinitis. In children, malodorous breath is also a notable symptom. There is infrequent, mild, purulent nasal discharge that does not improve with treatment.

Only the infected sinuses are painful. Although the cough associated with rhinosinusitis occurs throughout the day, it is typically more noticeable in the morning after waking up as a result of the collected secretions that accumulate in the posterior pharynx over the course of the night. (13)

Infectious Rhinitis Causative agents
Bacterial Streptococcus Pneumoniae, Hemophilus Influenzae, a-hemolytic and b-hemolytic Streptococci, Staphylococcus Aureus, Klebsiella species, anaerobes, S. Anginosus and methicillin-resistant S. Aureus (MRSA)
Viral Rhinovirus, Coronavirus, Adenovirus, Parainfluenza

Virus, Respiratory Syncytial Virus (RSV), Enterovirus.


Untreated bacterial rhinosinusitis can lead to a number of serious side effects, including cellulitis in orbit, osteitis of the sinus bones, meningitis, and brain abscess or infection of the intracranial cavernous sinus.

Amoxicillin-clavulanate is the first choice of antimicrobial agent in empiric treatment, followed by Doxycycline, Clindamycin, or an oral Cephalosporin. Quinolones are reserved for non-responsive patients. Treatment is continued for 5-7 days in adults and 10-14 days in children. Intranasal corticosteroids can also be used in patients with allergic rhinitis.

Subacute inflammatory or contagious viral rhinitis frequently progresses to chronic rhinitis. Prolonged inflammation may be exacerbated by low humidity and airborne allergens.

Chronic atrophic rhinitis is a unique kind of chronic rhinitis that is characterized by extensive underlying bone atrophy and sclerosis as well as gradual atrophy of the nasal mucosa. The lamina propria is diminished in size and vascularity, and the mucous membrane transforms from ciliated pseudostratified columnar epithelium to stratified squamous epithelium. Numerous symptoms, including fetor, crusting, nasal blockage, epistaxis, anosmia, and even the degeneration of soft tissues and cartilages, are present in both primary and secondary chronic atrophic rhinitis.

Treatment of chronic rhinitis is done by using nasal irrigation, glucose-glycerin or liquid paraffin nasal drops, topical and systemic antibiotics, vasodilators, estrogens, and vitamins A and D can also be administered orally. (15)

Clinical Features Bacterial




Duration of symptoms and


≥10 days 7–10 days


Fever ≥39°C P O
Purulent nasal discharge


Lasting for 3 or more days



Facial pain lasting for 3 or more days P O
New onset of symptoms after initial improvement




Another important AURTI in which the pharyngeal mucosa becomes inflamed and swollen. A painful throat is the predominant symptom of acute pharyngitis. Fever, headache, joint and muscle pains, skin rashes, and enlarged lymph nodes in the neck are signs and symptoms that may appear. Examination reveals tonsillar enlargement, exudates, sometimes mucosal erosions and vesicles, conjunctivitis, and cutaneous rash in addition to pharyngeal erythema.

The recommended course of treatment for streptococcal tonsillopharyngitis is a 10-day course of antibiotic therapy with penicillin. Other beta-lactams (such as amoxicillin and cephalosporins), macrolides, and clindamycin are alternatives to the “gold” standard. (16)

Viral pharyngitis cases are self-limiting within 7-10 days. Hydration, sufficient calorie intake, moderate physical exercise, antipyretics, and topical analgesics are all components of supportive care.

Infectious Pharyngitis Causative agent
Bacterial group A β -hemolytic Streptococcus

(S. Pyogenes)

Viral Rhinovirus, and Influenza A and B, enteroviruses, Epstein-Barr virus (EBV), and HIV.

Herpangina (Coxsackie virus A16, Coxsackie virus

B, enterovirus 71, echovirus, Parechovirus 1, Adenovirus, and Herpes Simplex Virus)

Infectious Mononucleosis (EBV infections)


Bacteremia, or the direct invasion of the epithelium by microbial pathogens, causes epiglottis infection. It may also involve cellulitis of the epiglottis, aryepiglottic folds, and other nearby tissues. The posterior wall of the nasopharynx is the main source of germs like H. influenzae, S. Pneumoniae, S. Aureus, and beta-hemolytic Streptococci. Sore throat, dysphagia, voice loss, inspiratory stridor, fever, anxiety, dyspnea, tachypnea, and cyanosis are some of the symptoms and warning indications. Treatment is based on maintaining the patency of the airways. A child with dyspnea, may frequently sit up straight, lean forward, stretch neck, and keep mouth open to improve airflow (tripod position). (18)


A broad viral or bacterial upper respiratory tract illness is more prevalent, but acute laryngitis can also happen on its own or in isolation. It starts with a dry cough, hoarseness (ranging from mild to total loss of voice), discomfort while speaking or swallowing, fever, malaise, and variable degrees of laryngeal edema. Vocal cords with circular swelling borders and exudates are red, inflamed, and occasionally hemorrhagic are observed through indirect laryngoscopy. The condition is self-limiting resolving within 7 days.

Hoarseness is typically the sole symptom of persistent laryngitis that lasts >3 weeks. Subacute classification might occasionally be useful when the clinical presentation falls between the acute and chronic subtypes. (19)

Infectious Laryngitis Causative agent
Viral •       Parainfluenza viruses

•       RSV

•       Measles

•       Varicella-zoster

·       Rhinovirus

•       Influenza A, B, C

•       Adenoviruses


Bacterial •       Streptococcus Pneumoniae

•       Klebsiella Pneumoniae

•       Staphylococcus Aureus

•       Diphtheria (Corynebacterium Diphtheriae, Corynebacterium Ulcerans)

•       Tuberculosis (Mycobacterium tuberculosis)

•       Hemophilus Influenzae type B

•       beta-hemolytic Streptococci

•       Moraxella Catarrhalis

•       Syphilis (Treponema pallidum)


Fungal •       Candida Albicans

•       Blastomyces Dermatitidis

•       Histoplasma Capsulatum

•       Cryptococcus Neoformans


Noninfectious laryngitis


•       Toxic agents

•       Alcoholism

•       Smoking,

•       Drugs (crack)

•       Allergy

•       Gerd

•       Laryngeal involvement of rheumatoid arthritis

•       SLE

•       Hypothyroidism

•       Angioneurotic edema



The most prevalent illness in the general population is an acute respiratory tract infection, which has significant societal repercussions including lost work time. The majority of AURTIs are brought on by viruses. More frequently than not, protracted or chronic infections that are attached to original viral illnesses are caused by bacterial pathogens.

The majority of the time, a physical exam and symptom identification serve as the basis for the diagnostic workup in instances with acute infections. In cases of protracted and chronic illness as well as in rare situations such as streptococcal pharyngitis, epiglottitis, and mononucleosis, further diagnostic testing should be done.

The majority of AURTIs are self-limiting and don’t need any special care. Tracheitis, bacterial sinusitis, otitis media, streptococcal pharyngitis, and chronic bacterial infections should all be treated with antibiotics.

See Also

Acute Abdomen

Approach to the Patient With Acute Vestibular Symptoms

Nephrolithiasis in Adults

Distal Radius Fractures in Adults

Diagnosis and Management of Vulvovaginitis

Diagnosis and Management of Anaphylaxis in Adults

Acute Uncomplicated Pyelonephritis in Adults


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