New Study Reveals How Influenza Virus Quietly Wreaks Havoc Beyond the Lungs in Viral Sepsis
Nikhil Prasad Fact checked by:Thailand Medical News Team May 14, 2025 9 hours, 21 minutes ago
Medical News: A major new discovery by researchers from the China-Japan Friendship Hospital and Capital Medical University in Beijing is changing the way scientists and doctors understand how severe influenza infections lead to deadly complications beyond the lungs. Their work sheds new light on a condition called viral sepsis, where a viral infection doesn't just cause pneumonia but triggers widespread organ damage throughout the body.
New Study Reveals How Influenza Virus Quietly Wreaks Havoc Beyond the Lungs in Viral Sepsis
In the past, most attention was focused on how influenza A virus (IAV) affects the lungs. However, this
Medical News report reveals that the virus can escape the lungs, enter the bloodstream, and infect other vital organs like the liver and spleen. This viral spread—called viraemia—is now being seen as a direct contributor to damage in tissues beyond the respiratory system.
Virus Spreads Through Blood and Infects Other Organs
Using carefully constructed mouse models, the research team administered the H1N1 PR8 strain of influenza to simulate both mild and lethal infections. In some mice, the virus was found not just in the lungs but also in the liver, spleen, heart, and kidneys. They even detected live virus particles in the bloodstream, platelets, and blood cells.
Interestingly, the most significant viral presence was seen in the liver and spleen, with strong signs of liver damage. Researchers also noted spleen atrophy and changes in immune cells that are essential for fighting infections. The virus was rarely found in the kidneys, suggesting that different organs are affected differently depending on how susceptible they are to infection.
To prove the virus was truly infecting liver cells, scientists used fluorescent imaging to track viral proteins inside the organ’s cells. When they interfered with the liver's ability to absorb the virus by targeting a gene involved in viral entry, liver damage markers in the blood improved significantly—further proof that the virus itself, not just the body’s immune reaction, was causing harm.
How Viral Sepsis Is Different from Bacterial Sepsis
The study compared viral sepsis (VS) to bacterial sepsis (BS), which is caused by bacteria like Streptococcus pneumoniae. In bacterial cases, researchers found extensive damage in multiple organs—heart, liver, and kidneys—along with high levels of inflammatory cytokines. But in viral sepsis, despite similarly high inflammation levels, organ damage was mostly confined to the lungs, liver, and spleen. The kidneys remained largely unaffected, suggesting the virus selectively targets certain tissues.
This finding is crucial because it challenges the long-standing belief that inflammation alone drives organ damage in sepsis. Instead, it suggests that the virus’s ability to enter and replicate in specific organs plays a major role in how and where damage occurs.
g>Immune Cell Breakdown and Lung Damage
Another part of the study used single-cell RNA sequencing to analyze how different lung and liver cells responded to infection over time. Researchers discovered a drop in crucial lung cell populations like epithelial and endothelial cells. These are the cells that form protective barriers and help the lungs absorb oxygen.
The data showed the virus infects and kills these cells through a process called PANoptosis—a deadly combination of three types of cell death. The collapse of these cells breaks down the lungs' structure and makes it easier for the virus to spread elsewhere in the body. Additionally, the immune response was overwhelmed in lethal cases, with an excess of inflammatory cells but not enough protective T cells or antibodies to clear the virus.
Conclusion
This groundbreaking study reveals that in severe influenza infections, the virus doesn’t just damage the lungs—it travels through the blood and attacks other organs like the liver and spleen. It does so not only through triggering inflammation but also by directly infecting cells in those tissues. These findings could help explain why some people with the flu experience unexpected complications like liver damage or sudden immune collapse. They also point to the need for new therapies that can stop the virus from spreading through the bloodstream and targeting vulnerable organs. In the future, better diagnostics and treatments for viral sepsis may save lives by stopping the hidden damage before it becomes fatal.
The study was conducted by scientists from the China-Japan Friendship Hospital, Capital Medical University, Peking Union Medical College, Tsinghua University-Peking University Joint Center for Life Sciences, and other key Chinese institutions.
The study findings were published in the peer reviewed journal: eBioMedicine
https://www.sciencedirect.com/science/article/pii/S2352396425001823
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https://www.thailandmedical.news/articles/influenza-or-flu
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