As the world continues to grapple with the consequences of the COVID-19 pandemic, another potential health crisis is on the horizon: coinfection with influenza and SARS-CoV-2. While each virus poses significant health risks on its own, their interactions within the human respiratory system may worsen disease, raising concerns about how these pathogens affect each other when they coexist. Recent research by Professor Narasaraju Teluguakula and colleagues explores this interaction and is published in the journal Viruses in 2024.
The study draws attention to an alarming phenomenon: When the two viruses infect the lungs at the same time, they can lead to more severe respiratory illness. Professor Teluguakula discussed the risk of coinfection and how it affects the survival and replication of both viruses with co-researchers from the University of Tennessee, Adichunchanagiri University in India and the National University of Singapore. As Professor Teluguakula points out, “Influenza coinfections are associated with increased morbidity and mortality in patients with COVID-19, suggesting synergistic effects that exacerbate lung disease and worsen clinical outcomes.” Their article highlights the importance of understanding influenza season The dynamics between these two viral pathogens are urgently needed.
Influenza viruses and SARS-CoV-2 viruses share several key characteristics—they are both single-stranded RNA viruses that infect the human respiratory tract and have overlapping modes of transmission. However, their interactions in the pulmonary environment remain complex. Clinical data on co-infected cases are inconclusive, with some patients showing increased severity of symptoms and others experiencing milder or no changes in outcomes. However, it is clear that both viruses can amplify the immune system’s inflammatory response, leading to increased lung damage and even organ failure.
An important finding is that influenza infection can change the behavior of SARS-CoV-2 in the lungs. In laboratory experiments, the influenza virus was found to replicate faster in lung cells, outcompeting SARS-CoV-2. This competitive inhibition could reduce the viral load of SARS-CoV-2 and thus may provide some protection against severe COVID-19. However, this is not always the case clinically, as influenza also upregulates receptors such as ACE2, which are critical for SARS-CoV-2 to enter cells, thereby promoting viral spread.
Interestingly, Professor Teluguakula and his team emphasize that co-infections can sometimes create lethal synergies between viruses. For example, in their study, co-infected animals showed increased inflammation, prolonged pneumonia, and worsening lung pathology compared with animals infected with only one virus. The phenomenon appears to be driven by the ability of both viruses to trigger an excessive immune response, often leading to acute respiratory distress syndrome (ARDS), a life-threatening disease. “The coexistence of two pathogens in the lungs may lead to an overwhelming inflammatory response, damaging alveolar structure and exacerbating pathophysiological consequences,” said Professor Teluguakula.
This dual viral threat has significant public health implications, especially during the winter when influenza typically surges. Research data suggests that patients, especially older adults and immunocompromised patients, are at higher risk for serious consequences if they are concurrently infected. The researchers also noted that some case reports suggest that co-infections lead to increased ICU admissions, longer hospital stays, and increased mortality.
Vaccination becomes a key strategy to mitigate the risks posed by this dual threat. The study highlights the potential protective effect of influenza vaccines against severe COVID-19 outcomes. “Annual influenza vaccination can significantly reduce ICU admissions and may even provide some protection against SARS-CoV-2,” said Professor Teluguakula, citing clinical studies showing influenza vaccination is associated with better COVID-19 outcomes. There is a correlation between them. The findings offer a glimmer of hope that widespread vaccination campaigns can help reduce the severity of mixed infection cases, especially during flu season.
Overall, Professor Teluguakula and colleagues highlight the need for more research to better understand the complex interactions between the two viruses. As influenza and SARS-CoV-2 are expected to continue circulating in the global population, future research will be needed to explore new treatment strategies and improved diagnostic tools to manage cases of coinfection. They stressed that while co-infections can be fatal, they are also preventable through vigilant public health measures such as vaccination, early detection and appropriate medical intervention. As we move into the future, understanding the interactions between these pathogens will be critical to reducing the burden of respiratory diseases on global health systems.
Journal reference
Teluguakula, N., Chow, VTK, Pandareesh, MD, Dasegowda, V., Kurrapotula, V., Gopegowda, SM, Radic, M.”SARS-CoV-2 and influenza co-infections: Fair play or sinister marriage? Virus2024-16-793.
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About the author
Dr. Narasaraju Teluguakula He received his PhD in Virology in 2002 from the Department of Microbiology, Osmania University, Hyderabad, India. (ORCID). ) in 2010 at a center funded by Oklahoma State University, Stillwater, Oklahoma, USA. Professor of Microbiology at the Institute and School of Natural Sciences. He has been engaged in research on “respiratory and infectious diseases” for more than 20 years. His laboratory is focused on understanding the pulmonary pathophysiology of influenza and SARS-CoV-2 viral infections. His research has identified multiple mechanisms by which neutrophils and the neutrophil extracellular traps (NETs) they release play a role in lethal influenza and SARS-CoV-2. He also serves as a grant reviewer for the U.S. Department of Defense (DoD) and the U.S. National Prok Committee. He has published more than 50 peer-reviewed articles and editorial columns in high-impact medical and scientific journals.
Dr. Zhou Dekang is a medical virologist and molecular biologist with MD, PhD, FRCPath, MBBS and MSc qualifications. Currently, he serves as Associate Professor of Microbiology and Principal Investigator of the Host-Pathogen Interaction Laboratory at the Yong Loo Lin School of Medicine at the National University of Singapore (NUS). Dr. Zhou has served as the President of the Asia-Pacific Society of Medical Virology and the President of the Virology Section of the International Society for Chemotherapy. He has received several awards and honors (including Murex Virologist Award for Rapid Viral Diagnosis, National University of Singapore Special Recognition Award and Faculty Research Excellence Award, Singapore Pathology Society – Becton Dickinson Award, 6th Asia – Tan Yew Cheong Lecture) Pacific Medical Virology academic conference). His research interests focus on the molecular genetics and infectomics of viruses/diseases such as influenza, enterovirus 71, dengue fever, SARS coronavirus, and human herpesvirus 6. articles.
Dr. MG Shivaramu, Dean and Dean of Health Sciences (Medicine), Adichunchanagiri Institute of Medical Sciences (AIMS), Karnataka, India, is a distinguished leader in medical education and healthcare. He holds a PhD in Forensic Medicine from Karnataka University, India. He has been instrumental in the academic, administrative and financial management of the institution and has received accreditation from national regulatory boards such as the National Accreditation Board for Hospitals and Healthcare Providers (NABH) and the National Accreditation Board for Testing and Calibration Laboratories (NABH ). Under his leadership, undergraduate and graduate enrollment was expanded, a mentorship system was established, and a research culture was promoted among students and faculty. Dr. Shivaramu is a distinguished researcher and educator specializing in forensic science and medical education technology. He was recognized for his efforts in improving the quality of education and research at AIMS, bringing notable rankings and awards to the institution. Dr. Shivaramu continues to contribute to the field through numerous publications and active participation in professional societies. He has also served on several public health councils and committees at the regional and national levels.
