An ARI is an infection affecting the upper or lower respiratory tract that lasts less than 30 days.^[1] The upper respiratory tract includes the nose, sinuses, middle ear, pharynx (throat), and larynx (voice box), while the lower respiratory tract includes the trachea and the bronchi, bronchioles, and alveoli of the lungs (the alveoli are where the oxygen and carbon dioxide exchange occurs in the body). Upper respiratory tract infections are the most common ARIs and include the common cold, sinusitis, tonsillitis, pharyngitis (sore throat), otitis media (ear infection), and laryngitis.^[2][3] Lower respiratory tract infections tend to be more serious and include pneumonia, acute bronchitis, bronchiolitis, and bacterial/fungal exacerbations of chronic obstructive pulmonary disease.^[3] Some ARIs (e.g., the flu, COVID-19) can affect both the upper and lower respiratory tract, depending on their severity.^[4]

The signs and symptoms of an ARI will depend on the part of the respiratory tract affected and the severity of the infection.

Common symptoms of ARIs include nasal congestion, runny nose, sore throat, facial pressure, sneezing, cough, phlegm, headache, muscle/body aches, tiredness, and fever. When the infection affects the lower respiratory tract, it may also cause shortness of breath, chest pain, and wheezing.^[3][4] Symptoms usually resolve within 2 to 10 days, though sometimes cough and nasal discharge can persist for several weeks.^[5]

A clinician may notice certain signs of an ARI during an examination, such as inflammation in the throat or ears, crackling and wheezing sounds in the lungs, increased levels of white blood cells, reduced blood oxygen levels, or abnormalities on a chest x-ray.^[6]

ARIs are often diagnosed based on clinical symptoms alone. Sometimes swabs of the throat or nose, or sputum (phlegm) samples may be used to identify the organism causing the infection, which can help guide treatment.^[7] A clinician may also perform a physical exam, including a visual check of the throat and ears, as well as using a stethoscope to listen to the lungs. Further testing, including blood work or a chest x-ray, can help determine the severity of the infection.^[6]

Most ARIs resolve on their own over time and do not require medical treatment, but it is always important to rest and stay hydrated to support recovery.^[6]

For symptom management in adults, the following may be helpful:^[8][9]

• Intranasal (i.e., sprayed up the nose) or oral decongestants (e.g., oxymetazoline, pseudoephedrine) can help reduce nasal congestion.
• Non-steroidal anti-inflammatory drugs (NSAIDs) (e.g., ibuprofen, naproxen) or acetaminophen can help with fever and sore throat.
• Antihistamines (e.g., diphenhydramine, chlorpheniramine) may slightly reduce sneezing and runny nose.

In the case of some ARIs, including flu and COVID-19, antiviral medications may be given to people at a higher risk of complications.^[7]

Although antibiotics are frequently prescribed for ARIs, they are usually not helpful because most ARIs are caused by viruses, not bacteria. Not only will antibiotics be ineffective for most ARIs, but they can also cause side effects like diarrhea and promote antibiotic-resistant bacteria that could cause a future bacterial infection that does not respond to standard antibiotics.^[5] However, if a clinician determines that an ARI is bacterial, antibiotic treatment can be life-saving.^[6]

Supplementation with specific micronutrients may help to reduce the risk and shorten the duration of an ARI. Vitamin C,^[3] vitamin D,^[10] and zinc^[11][12] supplementation show the most consistent benefits for ARI risk and duration.^[13]

For more information, see this page: Which Supplements Can Help Against Colds And the Flu?

Diet is connected to ARIs through immunity. Diets that are sufficient in energy (calories), micronutrients, and macronutrients are important for maintaining a robust immune system, which will help reduce the risk and severity of ARIs.^[14] Flavonoids, which are plant compounds that have antioxidant and immunomodulatory properties and are found in especially high quantities in tea, chocolate, capers, and oregano^[15] may be particularly helpful for maintaining immunity.^[16]

Vaccines are an important tool for preventing ARIs, although there is not a vaccine for all ARIs (e.g., the common cold). Vaccination can protect against (COVID-19), influenza (flu), pneumococcal disease (pneumonia), and pertussis (whooping cough).^[17]

In general, most ARIs are caused by viruses. Common respiratory viruses include rhinovirus, respiratory syncytial virus (RSV), influenza virus, human coronavirus, SARS-CoV-2, and adenovirus, although others have been identified.^[3] A viral ARI can predispose someone to a secondary bacterial respiratory infection, which is when a bacterial infection (e.g., bacterial pneumonia) occurs during or after an initial infection with a virus.^[18] Other ARIs, such as pharyngitis (strep throat), sinusitis, otitis media, and pneumonia, can be caused by bacteria alone. Less often, an ARI may be caused by a fungus or parasite.^[19]

Many ARIs are contagious and can be transmitted between people through respiratory droplets or direct physical contact. When the microorganism is inhaled or comes into contact with the mucosal lining of the nose or eyes, it infects the cells of the respiratory mucosa and begins to multiply and spread.^[4] Both the infecting organism and the immune system’s response to the infection create the symptoms associated with an ARI.^[20]

Many respiratory infections follow seasonal variations, meaning they occur more often during certain times of the year.^[21]