Acute upper respiratory tract infection is a general term describing acute inflammation of the nasal cavity, sinus, pharynx, and larynx. The pathogens are mostly viruses, but also bacteria, as well as mixed infection. In general, the disease is self-limiting and presents with mild symptoms, short duration, and good prognosis. However, due to high incidence, it can not only affect work and daily life, but also sometimes lead to serious complications, especially in vulnerable populations such as individuals with underlying diseases, infants, pregnant women, and older adults. It is mildly contagious, and proper treatment and prevention are required.
Epidemiology
The disease is one of the most common infectious diseases in humans, mainly in winter and spring, mostly sporadic. The primary mode of transmission includes airborne droplets from sneezing of the infected individuals and contact with contaminated hands and objects. The pathogens are mostly viruses widely found in nature, and healthy individuals can carry these viruses. Immunity generated after infection is weak and short-lived, and there is also no cross-immunity between different viruses, so recurrence is often present.
Etiology and pathogenesis
There are approximately 200 types of viruses that can cause upper respiratory infections. On average, 2 - 4 infections in adults and 4 - 8 infections in preschool children occur every year. 70% - 80% patients are infected by viruses, mostly rhinoviruses, but also coronaviruses, adenoviruses, influenza and parainfluenza viruses, respiratory syncytial virus, echovirus, and coxsackieviruses. 20% - 30% of infections are caused by bacteria, and can be solitary or secondary to viral infection, mostly hemolytic streptococcus, but also Haemophilus influenzae, Streptococcus pneumoniae, staphylococcus, and occasionally Gram-negative bacilli. The onset after exposure to pathogens depends on the susceptibility of individuals. Rain exposure, cold exposure, sudden climate changes, overexertion, and cigarette smoking can reduce local respiratory defense function, leading to rapid replication of invading viruses or bacteria. Older adults, infants, immunocompromised hosts, and patients with chronic respiratory diseases such as asthma, chronic obstructive pulmonary disease, sinusitis, and tonsillitis are more susceptible.
Pathology
Pathological changes are inapparent, but epithelial damage may be present. The involvement of inflammatory cytokines leads to congested upper respiratory mucosa, mononuclear infiltration, and serous and mucous inflammatory exudation. Neutrophil infiltration and purulent discharge may occur in secondary bacterial infection. Local mucosal congestion causes clinically nasal congestion, pharyngeal pain, and hearing deterioration or otitis media resulting from eustachian tube edema. The respiratory epithelium damage and release of inflammatory cytokines into the bloodstream result in fever and generalized myalgia.
Clinical manifestations
Common cold, also known as acute rhinitis or upper respiratory catarrh, is caused by viral infection, with rapid onset, and is mainly manifested by nasal symptoms such as sneezing, nasal congestion, and clear watery nasal discharge, but also cough, pharyngeal pain, pharyngeal pruritus, burning sensation, and even postnasal drip. Nasal discharge thickens in 2 - 3 days, and may be accompanied by pharyngeal pain, headache, lacrimation, hypogeusia, respiratory disturbance, and hoarseness. Sometimes, hearing deterioration may be caused by eustachian tube inflammation. Fever, mild chills, and headache may be present in severe patients. Nasal congestion, edema, and discharge; and mild pharyngeal congestion can be seen on physical examination. Usually, the disease heals in 5 - 7 days, but complications may result in protracted course.
Acute viral pharyngeal pain is caused by rhinovirus, adenovirus, influenza virus, parainfluenza virus, enterovirus, and respiratory syncytial virus. Clinical manifestations include pharyngeal pruritus, burning sensation, mild pharyngeal pain, and rarely cough.
Acute laryngitis is mostly caused by influenza virus, parainfluenza virus, and adenovirus, and is characterized by dysphonia, dysarthria, pharyngeal pain, and cough that exacerbates pharyngeal pain. Laryngeal congestion, edema, and mild enlargement and tenderness of regional lymph nodes can be found on physical examination. Sometimes, wheezing can be heard.
Acute herpangina mainly occurs in summer, predominantly in children, occasionally in adults, and is caused by Coxsackievirus A and is manifested by severe pharyngeal pain and fever, lasting for a week. Pharyngeal congestion and grayish white blebs and superficial ulcers on the soft palate, uvula, pharynx, and tonsil surfaces, surrounded by red halo, can be visible on physical examination.
Acute pharyngoconjunctivitis occurs in summer, mainly in children, and the virus is transmitted through swimming. It is primarily caused by adenovirus and Coxsackievirus. Clinical presentation includes fever, pharyngeal pain, photophobia, lacrimation, and pharyngeal and conjunctival congestion, lasting for 4 - 6 days.
Acute pharyngotonsillitis is mostly caused by hemolytic streptococcus, followed by Haemophilus influenzae, pneumococcus, and staphylococcus. The clinical features are acute onset, severe pharyngeal pain, fever, chills, and body temperature over 39℃. Severe pharyngeal congestion, enlarged and congested tonsils covered by yellow purulent discharge, and sometimes enlarged and tender submandibular lymph nodes can be detected on physical examination.
Laboratory examination
Blood test
As a result of mostly viral infection, white blood cell count is normal or slightly declined, and lymphocyte ratio is increased. Increased white blood cell count, increased neutrophils, and left shift can be observed in bacterial infection.
Etiological test
On account of various virus types and lack of clear benefits in treatment from identifying the specific type, etiological test is generally not necessary. If needed, immunofluorescence, enzyme-linked immunosorbent assay, serological diagnosis, or viral isolation with nasal swabs or nasopharyngeal swabs can be used to determine the virus type. Bacterial culture can be used to identify the bacterial type, and antibiotic sensitivity test can improve clinical treatment.
Complications
Acute sinusitis, otitis media, and tracheobronchitis may be complicated in few patients. Secondary rheumatic fever and glomerulonephritis caused by hemolytic streptococcus may be present in patients with pharyngeal pain. Viral myocarditis can be complicated in few patients. Patients with underlying diseases such as COPD, asthma, and bronchiectasis may suffer from acute exacerbation. Heart failure may be aggravated in patients with cardiac insufficiency.
Diagnosis
On the basis of nasopharyngeal presentation in combination with routine blood test and negative chest x-ray, a clinical diagnosis can be established. Usually, there is no need for etiological diagnosis. Under exceptional circumstances, etiological examination can be conducted. It is necessary to differentiate from other diseases that initially present with cold-like symptoms.
Differential diagnosis
Allergic rhinitis
Allergic rhinitis presents with rapid onset, nasal mucosal congestion, increased discharge, sudden and continuous sneezing, nasal pruritus, nasal obstruction, excessive clear nasal discharge, and mild cough, but without fever. It is mainly caused by allergens such as dust mites, dust, animal fur, and low temperature. Symptoms subside within minutes to 1 - 2 hours after separating from the allergen. Pallor and edema of the nasal mucosa and increased eosinophils in nasal discharge can be found on examination. The allergen can be identified using skin sensitization test.
Influenza
Influenza is caused by influenza virus, usually sporadic, but occasionally epidemic. Viral mutation can cause epidemics. It presents with acute onset, mild nasal and pharyngeal symptoms, and severe systemic symptoms including high fever, generalized myalgia, and conjunctivitis. Rapid serum PCR for viral detection can be used for differential diagnosis.
Acute tracheobronchitis
Acute tracheobronchitis presents with cough, expectoration, and elevated white blood cell count. Nasal symptoms are mild, but increased lung markings can be seen on chest x-ray examination.
Other acute infectious diseases
Prodromal symptoms of some acute infectious diseases, such as measles, poliomyelitis, encephalitis, hepatitis, and myocarditis, can also be nasal congestion and headache. However, if respiratory manifestations subside and new presentation occurs within a week, necessary laboratory test should be conducted to avoid misdiagnosis.
Treatment
Since there are currently no specific antivirals, symptomatic treatment is the main regimen. Smoking cessation, good rest, abundant drinking, good indoor ventilation, and secondary bacterial infection prevention should be conducted.
Symptomatic treatment
Patients with acute cough, postnasal drip, and pharyngeal pain can be treated using pseudoephedrine to relieve nasal congestion, and topical nasal drops can be administered. Antipyretics and analgesics, such as acetaminophen and ibuprofen, can be added as needed. Aspirin is contraindicated in children, which can cause Reye syndrome. Aspirin is also contraindicated in patients with a history of asthma.
Antibiotic treatment
Antibiotics are not necessary for common cold. If there is evidence of bacterial infection such as elevated white blood cell count, purulent coating, yellow phlegm, and nasal discharge, penicillin, first-generation cephalosporins, macrolides, and quinolones can be selected on the basis of local epidemiological history and experiences. Quinolones are contraindicated in individuals under age 18.
Antiviral treatment
During epidemic, in high-risk populations such as older adults, patients with chronic underlying diseases, patients with immunodeficiency, and obese individuals (BMI ≥ 28 kg/m2), if diagnosed with influenza or coronavirus disease, it is recommended to start antiviral treatment as early as possible. Oseltamivir and baloxavir can be used for influenza virus infection, and nirmatrelvir, simnotrelvir, and deuremidevir hydrobromide can be used for coronavirus disease, which can reduce the risk of hospitalization and death in severe patients. There are not effective antiviral medications for other respiratory viruses, such as rhinovirus, respiratory syncytial virus, and adenovirus. To avoid abuse causing resistance or other adverse reactions, it is not recommended to use drugs without definite efficacy in mild patients.
Prevention
Isolation of the source of infection helps prevent transmission. Face masks and avoidance of crowded public places during outbreaks can reduce the risk of infection.