In most cases, the flu is harmless and can often be overcome within a few days without medical help. Nevertheless, the flu can also lead to death. However, this is mostly not due to the influenza virus itself, but to what is known as secondary bacterial pneumonia.
Until now, it was largely unknown why influenza infections contributed to an increased risk of bacterial pneumonia. Swedish researchers at the Karolinska Institute in Stockholm have now described important findings that lead to so-called superinfections. The study, which was published in the journal “PNAS“may also help research into Covid-19.
Pneumococcal infections as the leading cause of death worldwide
Pneumococcal infections are the most common cause of community-acquired pneumonia – the Karolinska Institute reports in a press release. This makes them one of the leading causes of death worldwide.
The researchers identified influenza-induced changes in the lower airways that affect the growth of pneumococci in the lungs. With the help of an animal model, they were able to determine that various nutrients and antioxidants such as vitamin C and other substances that normally protect cells are released from the blood, creating an environment in the lungs that encourages the growth of bacteria.
The bacteria eventually increase the production of the bacterial enzyme HtrA and so can adapt to the inflammatory environment. HtrA weakens the immune system and promotes bacterial growth in the influenza-infected airways.
New therapeutic approaches possible
The results of the study can now be used to find new therapies for double infections between the influenza virus and the pneumococcal bacteria. One possible strategy, for example, would be to use protease inhibitors to prevent pneumococci from growing in the lungs.
It has not yet been proven whether corona sufferers are also sensitive to such secondary bacterial infections. However, the Swedish researchers believe that similar mechanisms could be found in critically ill patients.