Some strains of the flu are more deadly than others. But a new treatment might block the chemical pathway that some strains use to kill their hosts.

Although the worst of the flu season is now behind us, the disease is still at large. Most prevalent this season is the influenza strain H1N1, also known as swine flu, which reached pandemic levels in 2009. Fortunately, if you’ve gotten this season’s flu vaccine, you’re protected against H1N1.

For those who did not get a flu shot, however, H1N1 remains a hazard. Since the beginning of the flu season in October, more than 7,400 people have been hospitalized for lab-confirmed influenza, with more than 60 percent of cases reported in people 18 to 64 years of age.

More than 60 children have died from the flu this year, and although the CDC doesn’t track the total number of flu deaths in adults, the percentage of all reported deaths that are caused by influenza has exceeded the epidemic threshold since January 11. These deaths occurred not just among the elderly and infirm, but also among young and otherwise healthy people.

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When the body’s immune system is fighting an infection, it uses chemicals called cytokines to activate immune cells. Although the exact cause is unknown, some viruses—including H1N1—can lead the body to produce an overabundance of cytokines, causing too many immune cells to flock to the infection site. This leads to a condition called a cytokine storm, which can cause inflammation or even permanent damage to the body.

“The cytokine storm is a dysregulated or overactive host response to infection,” said Hugh Rosen, M.D., Ph.D., of the Scripps Institute, in an interview with Healthline. “Cytokines are important in the control and sterilization of viruses, but if production is excessive, they contribute to collateral damage of normal tissues, making the illness worse.”

In the case of influenza, a cytokine storm fills the lungs with fluid and immune cells, damaging the lungs until the infected person can’t draw in enough air to breathe. For those fortunate enough to survive the cytokine storm, the lung damage can still lead to pneumonia, which claims many additional lives. Because a cytokine storm uses the body’s own defenses against it, healthy people are just as vulnerable as people with pre-existing diseases.

The CDC believes that the most dangerous influenza strains are mutant descendants of the 1918 Spanish flu pandemic, which infected one third of the world’s population and killed at least 50 million people. Influenza only has eleven genes, allowing it to mutate very rapidly, which is why you need a new, reformulated flu shot every year.

Because of this rapid mutation, strains can differ a great deal, and some strains are more likely to cause cytokine storm than others. There is some evidence that H1N1 and the bird flu strain H5N1 could cause cytokine storms in healthy patients.

“Influenza, by virtue of its genetic makeup, has more variability than some other viruses, and these genetic variations may excessively amplify the host response, causing a cytokine storm,” said Rosen.

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Rosen is the co-senior investigator of a study on a new chemical, CYM5442, which blocks the cytokine storm response in the body. The chemical targets a site in the body called S1PR1, which controls the activity of immune cells called lymphocytes and is involved in cytokine storms. By targeting these immune cells with CYM5442, scientists might be able to stop the feedback loop that leads to a deadly cytokine storm.

Currently, CYM5442 is not in clinical trials to treat influenza. “These are early proof of concept experiments to develop the basic science,” said Rosen. “Clinical translation must first do no harm and be really safe, and thus may lag five to 10 years behind these early discoveries.”

Rosen also told Healthline about another compound called RPC-1063. This compound behaves similarly to CYM5442 and is currently being tested in clinical trials to treat two autoimmune diseases. In the case of autoimmune diseases, the immune system becomes overactive and attacks the body instead of fighting infections.

RPC-1063 is in Phase III clinical trials to treat multiple sclerosis, in which nerve cells in the brian and spinal cord are damaged, and in Phase II trials for ulcerative colitis, which damages the colon.

Flu season is expected to last for at least another month. Here’s how you can avoid the infection:

  • Get vaccinated. This year’s vaccine protects against three common types of influenza: H1N1, H3N2, and one type of influenza B. If you got last year’s vaccine, it’s still important to get this year’s, as the virus mutates every year.
  • Wash your hands. Use hot water and soap and scrub for at least 30 seconds to ensure that your hands are germ-free. If you’re out of the house, avoid touching your mouth and eyes, since a contaminated surface you’ve touched could make you sick.
  • If you’re sick, stay home. Although your co-workers or classmates may be healthy, they might have small children, elderly relatives, or immune-impaired family members at home. By exposing them to the flu, you put others at risk. Take a break and focus on your own healing.
  • Avoid droplet spread. Avoid coughing or sneezing on other people. If you have to sneeze, sneeze into your elbow instead of into your hands, so that your hands stay clean.

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