A study coming out of Children’s Hospital of Philadelphia, Pennsylvania, has found that the influenza virus manages to dysregulate the immune system, allowing other infections to thrive in the body. This discovery, coming at an opportune time as the world battles the new H1N1 flu outbreak, may be the first step in understanding why the flu can cause such high mortality rates in normally healthy individuals.
The 1918 flu pandemic, which killed 50 million people worldwide, appeared to affect young people more than other ages. This facet of the outbreak was dissimilar to seasonal flu deaths which tend to count the elderly and very young among its victims. How the flu virus manages to cause such severe sicknesses in some people, and why it sometimes affects healthy people and other times the elderly or very young, has long been a medical mystery.
In order to study the effect the flu virus has on the immune system, Dr. Kathleen Sullivan, lead researcher, took plasma samples from those suffering from severe flu, mild flu, an unrelated respiratory disease, and healthy patients. Sullivan studied the levels of cytokines, proteins that mark an activation of the immune system. And, “although they found elevated levels of cytokines [in flu patients], they also found a decreased response of toll-like receptors, which activate immune cell responses as a result of invading microbes.” [EurkeAlert]
When diseases that quiet the immune system infect a person, other opportunistic diseases such as bacterial infection can attack, leading to a more severe illness and even death. While some patients manage to steer clear of other infections, those that are afflicted by them will have a much more difficult time overcoming both the flu and the new disease. The ‘paralysis’ of the immune system “might explain why one quarter of children who die from influenza, die from a bacterial infection occurring on top of the virus.” [EurkeAlert]
In the paper, published in Journal of Leukocyte Biology, the authors sate that the “data suggest most cases of severe influenza occurring in previously healthy children are not associated with a specific innate immunologic deficit.” [JLB] In other words, anyone can be infected even if he or she has a perfectly functioning immune system. While those with innately weak immune systems may be predisposed to more severe infections, everyone is at risk for dysregulation of the immune system by the flu virus.
The work is only preliminary. But knowing what happens to the immune system may lead to more effective treatments for the flu. Sullivan said, “We have a very limited understanding of why some people who get influenza simply have a bad cold and other people become very sick and even die. The results of this study give us a much better sense of the mechanisms underlying bacterial infections arising on top of the viral infection." [EurekAlert]
Comments
I think comparing it to HIV is reaching a bit. Yes, the flu makes people somewhat more susceptible to other infections, but the same is true of many other viral infections. If the flu is immunosuppressive, it's very different from, and much less severe than, HIV.
I don't find "dysregulate" in the dictionary.
Good point, MJ. HIV was the first immune suppressing disease that came to mind, but admittedly, a bit far reaching. Good comment.
And to Jim:
From Merriam-Webster: dysregulate: impairment of a physiological regulatory mechanism (as that governing metabolism, immune response, or organ function)
This isn't news to me. Any attack of flu, or a cold for that matter, can lead to more severe secondary infections. My mother's remedy was simple: gargling with hot salt water. Bacteria can't multiply in a saline solution. What do you want to bet that the geniuses who did this study won't bother to even consider such a simple and mundane solution?
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