New Study Expands Understanding of Influenza-associated Complications

Key Takeaways for the People with Underlying Medical Conditions
  • Everyone 6 months and older should receive an influenza vaccine every year to protect against influenza and the severe outcomes that can be associated with influenza illness.
  • Influenza vaccination is especially important for people at high risk for serious influenza complications, including those with underlying medical conditions.

Flu is a respiratory disease and respiratory complications, such as pneumonia, are the most common reason for people to be hospitalized from flu. However, a study published in JAMA Network Openexternal icon sheds new light on the number and impact of people hospitalized from flu for non-respiratory complications. Researchers looked at medical records of over 76,000 adult flu patients hospitalized from 2010 through 2018.  Results showed that most had an acute respiratory complication as expected, but, nearly half also had a non-respiratory complication, and 5% of patients only experienced a non-respiratory complication from their flu infection. The most common acute non-respiratory complications reported were sepsis, acute kidney injury, and acute cardiovascular events.

In fact, besides pneumonia, which was the most common acute respiratory complication (occurring in 36% of patients), the next two most commonly occurring influenza complications were non-respiratory complications: sepsis (23%) and acute kidney injury (20%). Patients with pneumonia, sepsis and acute kidney injury, had a high frequency of severe hospital outcomes, including intensive care unit (ICU) admission and in-hospital mortality, underscoring the fact that non-respiratory complications can be just as severe as a respiratory complication. Additionally, in many cases, severe outcomes and the demand for hospital resources was greater for cases with non-respiratory complications. The study also found that patients with only acute non-respiratory complications were less likely to receive antivirals (81%) compared to those with respiratory complications (89%), suggesting possible missed opportunities to more effectively manage influenza infections in hospitalized patients. Understanding the frequency and impact of both respiratory and non-respiratory complications from flu provides a clearer picture of the full burden and impact of influenza disease.

Key Takeaways for Health Care Professionals
  • Health care providers should be aware of the range of influenza related complications that can occur in patients hospitalized with influenza.
  • Early antiviral treatment is important for all hospitalized patients, and especially for those at high risk for influenza complications.

This study also highlights the increased risk of influenza-associated complications for people with underlying medical conditions. Among patients with at least one acute respiratory complication, 43% had an underlying respiratory medical condition, such as asthma or chronic obstructive pulmonary disease (COPD). Among patients with an acute non-respiratory complication, there was a significantly higher frequency of underlying medical conditions, including metabolic (52%), cardiovascular (51%), renal (33%), neurological (30%), immunosuppressive (19%), hepatic (7%), and hematologic (6%). This new evidence emphasizes the increased risk of influenza complications for people with underlying medical conditions and provides a reminder as to why influenza vaccination and the prompt use of antiviral medication is so important for people with underlying health conditions.

These findings should serve as a reminder to health care providers of the vast array of complications that can result from influenza. Health care providers should be aware and consider the range of respiratory and non-respiratory complications that can occur in patients hospitalized with influenza.