Respiratory Virus Surge: Diagnosing COVID-19 vs RSV, Flu

Medscape | By Kelly Wairimu Davis

Amid the current wave of winter respiratory virus cases, influenza (types A and B) leads the way with the highest number of emergency room visits, followed closely by COVID-19, thanks to the JN.1 variant, and respiratory syncytial virus (RSV). With various similarities and differences in disease presentations, how challenging is it for physicians to distinguish between, diagnose, and treat COVID-19 vs RSV and influenza?

While these three respiratory viruses often have similar presentations, you may often find that patients with COVID-19 experience more fever, dry cough, and labored breathing, according to Cyrus Munguti, MD, assistant professor of medicine at KU Medical Center and hospitalist at Wesley Medical Center, Wichita, Kansas. 

"COVID-19 patients tend to have trouble breathing because the alveoli are affected and get inflammation and fluid accumulating in the lungs, and they end up having little to no oxygen," said Munguti. "When we check their vital signs, patients with COVID tend to have hypoxemia [meaning saturations are less than 88% or 90% depending on the guidelines you follow]."

Patients with RSV and influenza tend to have more upper respiratory symptoms, like runny nose, sternutation — which later can progress to a cough in the upper airways, Munguti said. Unlike with COVID-19, patients with RSV and influenza — generally until they are very sick — often do not experience hypoxemia.

Inflammation in the airways can form as a result of all three viruses. Furthermore, bacteria that live in these airways could lead to a secondary bacterial infection in the upper respiratory and lower respiratory tracts — which could then cause pneumonia, Munguti said.

Another note: Changes in COVID-19 variants over the years have made it increasingly difficult to differentiate COVID-19 symptoms from those of RSV and influenza, according to Panagis Galiatsatos, MD, pulmonologist and associate professor at Johns Hopkins Medicine. "The Alpha through Delta variants really were a lot more lung tissue invading," Galiatsatos said. "With the COVID-19 Omicron family — its capabilities are similar to what flu and RSV have done over the years. It's more airway-invading."…

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