Influenza makes people vulnerable to bacterial infection
Researchers at Sweden’s Karolinska Institutet have described findings leading to so-called “superinfections”, it can also contribute to research onCovid-19.
- Influenza is caused by a virus, but the most common cause of death in influenza patients is secondary pneumonia caused by bacteria, rather than the influenza virus itself.
- While this is well known, what is largely unknown is why influenza infections lead to an increased risk of bacterial pneumonia.
- The Spanish flu, which was an influenza pandemic that swept across the world in 1918–20.
- Unlike many other pandemics, the Spanish flu disproportionately hit young healthy adults.
- And one important reason for this was “superinfections” caused by bacteria, in particular pneumococci.
- Pneumococcal infections are the most common cause of community-acquired pneumonia and a leading global cause of death.
- A prior influenza virus infection is often followed by a pneumococcal infection. In the new study, the mechanisms behind this increased susceptibility: influenza induces changes in the lower airways that affect the growth of pneumococci in the lungs.
- Research found that different nutrients and antioxidants, such as vitamin C, leak from the blood.
- This creates an environment in the lungs that favours growth of the bacteria.
- The bacteria adapt to the inflammatory environment by increasing the production of an enzyme called HtrA.
- The presence of HtrA weakens the immune system and promotes bacterial growth in the influenza-infected airways.
- The researchers suggest the results could be used to find new therapies for double infections between the influenza virus and pneumococcal bacteria.
- A possible strategy can therefore be use of protease inhibitors to prevent pneumococcal growth in the lungs.