Influenza: Clinical sciences

Influenza is a highly transmissible viral infection that can primarily affect the upper and lower respiratory tract. It spreads via aerosols and directly infects the respiratory epithelium, causing inflammation. If you suspect influenza, you should determine whether your patient has a high risk of complications, and perform viral testing to confirm the diagnosis and guide treatment decisions.

Now, if a patient presents with signs and symptoms of influenza, you should first perform an ABCDE assessment to determine if they are unstable or stable. If they’re unstable, begin acute management. First stabilize their airway, breathing, and circulation. Next, obtain IV access and put your patient on continuous vital sign monitoring including heart rate, blood pressure, and pulse oximetry. Provide supplemental oxygen if they’re hypoxic, to maintain oxygen saturation above 90%.

Now let's go back to the ABCDE assessment and discuss the approach to stable patients. First, perform a focused history and physical examination. Your patient may report a sudden onset of fever, chills, myalgia, malaise, and headache. Additionally, local inflammation can result in dry cough, sore throat, and rhinorrhea. Your patient might also report exposure to a possible influenza contact within the previous 1 to 4 days, especially if there’s high transmission of influenza in the community.

Physical exam may reveal nonpurulent conjunctivitis, diaphoresis, and pharyngeal erythema, as well as abnormal lung sounds, such as crackles, rhonchi or wheezing.

At this point you can suspect influenza, so your next step is to assess whether your patient presents with high-risk features. Individuals are considered to be at high risk if they have chronic medical conditions, like diabetes, obesity, or heart disease, or if they are immunocompromised, like those with HIV or an organ transplant. In addition, certain populations are at higher risk, such as patients who are pregnant or less than 2 weeks postpartum, and those over the age of 65. Finally, individuals with severe or progressive symptoms, as well as patients who are currently hospitalized or living in a chronic care facility are also at high risk for influenza complications.