Breaking Research Throws Light on COVID, Flu, and RSV Co-Infections

At the 2023 AACC Annual Scientific Meeting & Clinical Lab Expo, researchers presented new data on co-infection rates of SARS-CoV-2, influenza, and respiratory syncytial virus (RSV) in the United States. This study provides one of the earliest insights into the interrelationship between these prevalent yet potentially lethal viruses and could contribute to enhanced diagnosis and patient management for these illnesses. After analyzing over 26,000 respiratory tests from US adults and children in late 2022, the researchers found co-infections in over 1% of positive cases, with the rate being particularly high in individuals below 21 years. These findings could impact how clinicians approach testing for respiratory diseases during future epidemics and seasonal outbreaks.

Respiratory viruses like RSV place substantial strain on public health systems. The likelihood of co-infections increases during multiple outbreaks of respiratory diseases, such as in the winter flu season. Patients with co-infections run a higher risk of developing severe disease and experiencing treatment complications, underlining the importance of understanding the prevalence of co-infections within the general population. Co-infections can be especially challenging during an epidemic. For instance, a surge in RSV cases in the US towards the end of 2022 coincided with the continuous spread of COVID-19 and the onset of the seasonal flu. However, there has been very less data defining co-infection rates during this RSV outbreak, which until recently lacked a vaccine.

Now, scientists at Quest Diagnostics (Marlborough, MA, USA) have presented one of the first comprehensive studies on co-infection rates in the US amidst the COVID-19 pandemic. In a retrospective study, they examined 26,657 respiratory tests collected from a clinical laboratory over a 107-day period in the fall of 2022, which included 9,800 samples from patients below 21 years. Using the Roche cobas and Cepheid Xpert platforms, they tested these samples for RSV, SARS-CoV-2, and influenza A/B.

The tests demonstrated that co-infections with two or more of these viruses occurred in 1.33% of positive cases and in .55% of all samples studied. The positivity rates varied depending on the viruses involved, ranging from .38% in adults for both SARS-CoV-2 and RSV to 2.28% in adults for both influenza A and SARS-CoV-2. However, co-infection rates in the pediatric group surpassed those in the adult population for all three viruses. A striking 6% co-infection rate of SARS-CoV-2 and influenza A in those under 21 was observed, which echoed previous findings by the Centers for Disease Control and Prevention in hospitalized pediatric patients.

“As we experience more flu-seasons and future epidemics of respiratory viruses, we’ll be able to acquire more co-infection rate data,” said lead scientist George Pratt, Ph.D., at Quest Diagnostics. “Our current work would make a useful data point to help evaluate whether future co-infection rates are shrinking or growing.”

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