Overview of Viral Respiratory Infections

• Usually history and physical examination and local epidemiology

• Sometimes diagnostic testing

Viral respiratory infections are typically diagnosed clinically based on symptoms and local epidemiology (1). In practice, diagnosing the syndrome based on symptoms and signs (eg, common cold) and infections that are common in a certain geographic area at that time is usually sufficient for most patients; identification of a specific pathogen is rarely necessary.

Diagnostic testing should be reserved for the following:

• Situations in which knowing the specific pathogen affects clinical management (eg, need for antivirals versus antibiotics, in patients with immunodeficiency)

• Epidemiologic surveillance (ie, identifying and determining the cause of an outbreak)

Pathogen identification can be important when specific antiviral therapy is indicated. Antiviral therapy is given for the following respiratory viruses and indications:

• Influenza: Patients or close contacts of patients at high risk of complications; may be given to average-risk patients with symptoms for < 48 hours (2)

• COVID-19: Patients at high risk of severe disease with symptoms for < 5 days (3)

• RSV infection: Specific, high-risk, immunocompromised patients (eg, post-allogeneic hematopoietic cell transplantation) (4)

Identifying the specific pathogen (particularly the influenza virus or RSV in hospitalized patients or patients residing in a facility) may also be important for infection and outbreak prevention and control in institutional settings.

Rapid point-of-care antigen-based and molecular diagnostic methods (eg, polymerase chain reaction [PCR]-based) diagnostic tests are available for influenza, RSV, and SARS-CoV-2. The rapid point-of-care antigen-based tests have lower sensitivity than PCR-based laboratory tests (5, 6). Point-of-care tests are typically reserved for cases when the clinical diagnosis is uncertain and:

• Antiviral therapy is being considered.

• Identification of the viral pathogen would prevent additional evaluation for or treatment of a bacterial infection.

• Identification of the viral pathogen would aid in infection prevention and control in the inpatient setting.

PCR-based detection of viral pathogens in a multiplex panel (or individually for influenza, RSV, and SARS-CoV-2) may be preferable for management because they are highly sensitive and widely available (6, 7).

Cell culture or serologic tests for viruses are sometimes available but are slower than PCR tests. They may be useful for epidemiologic surveillance.

• Supportive care

• Sometimes inhaled bronchodilators or glucocorticoids

• Sometimes antiviral medications

The treatment of viral respiratory infections is usually supportive (eg, rest; hydration; gargling; symptomatic relief of pain, fever, and congestion).

Antibiotics are ineffective for the treatment of infection caused by viral pathogens. Prophylaxis against secondary bacterial infections is not recommended. Antibiotics should be given only when secondary bacterial infections develop.

Aspirin should not be used in patients aged ≤ 18 years with a suspected viral respiratory tract infection because of the risk of development of Reye syndrome.

Some patients continue to cough for 3 to 8 weeks after resolution of an upper respiratory infection (1); these symptoms may lessen with use of an inhaled bronchodilator or inhaled corticosteroids (glucocorticoids), particularly in children with recurrent wheezing. (See Wheezing and Asthma in Infants and Young Children.)

In some patients, antiviral medications are useful:

• For influenza: Oseltamivir, baloxavir marboxil, and zanamivir are effective (2, 3).

• For COVID-19: Nirmatrelvir with ritonavir, remdesivir, or molnupiravir after onset of symptoms of COVID-19 may be considered to prevent progression to severe disease in high-risk patients, and remdesivir may be considered for severe COVID-19 (4).

• For RSV: Ribavirin, a guanosine analog that inhibits replication of many RNA and DNA viruses, may be considered for severely immunocompromised patients with lower respiratory tract infection due to RSV (5).

Prevention of viral respiratory infections is with immunizations or monoclonal antibodies.

Immunization against RSV, COVID-19, and influenza is routinely recommended for the prevention of severe respiratory viral illnesses in most patients (1).

Nirsevimab and clesrovimab are monoclonal antibodies used to prevent RSV infection in infants and young children (2). Palivizumab is not recommended for routine use. (See Prevention of RSV and hMPV.)