Understanding Why Certain Influenza Viruses Pose Greater Threats

Influenza viruses are responsible for seasonal flu outbreaks and can vary significantly in their severity. While most infections result in mild symptoms, some strains of influenza A can cause severe illness, including pneumonia and in some cases, death. A major factor behind this disparity is how these viruses interact with the human immune system.

Researchers at the Paul-Ehrlich-Institut examined eleven different influenza A virus strains, focusing on their effects on various human immune cells. Their investigation shed light on the mechanisms that make some influenza viruses more dangerous than others.

A key discovery was the role of specific immune cells called plasmacytoid dendritic cells, which rapidly produce large quantities of the antiviral molecule interferon-alpha (IFN-α) upon infection, regardless of the virus strain. However, the severity of the immune response depends on whether other immune cells, like myeloid dendritic cells and macrophages, are infected by the virus. Highly pathogenic strains can infect these cells, leading to increased production of interferons and a heightened immune response.

This exaggerated response, known as a cytokine storm, can cause extensive tissue damage and severe inflammation, contributing to the severity of the disease. The ability of certain influenza viruses to replicate within immune cells appears to be a crucial factor in triggering these dangerous immune reactions.

The findings help explain why some flu strains are more lethal and offer pathways for developing targeted therapies. Identifying which viruses can infect immune cells and induce cytokine storms can improve risk assessment and aid in designing effective interventions.

Overall, understanding the interaction between influenza viruses and the immune system enhances our ability to predict and combat severe flu infections, potentially saving lives through better prevention and treatment strategies.

Source: https://medicalxpress.com/news/2025-09-influenza-viruses-dangerous.html