Swine Flu article by Chicago Tribune
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The very young, elderly or sick may have a weak immune system that is unable to keep up with the virus or allows a second infection to take root, sometimes resulting in death. More than 30,000 Americans a year die from influenza-related illness, according to the Centers for Disease Control and Prevention.
Especially alarming to public health officials are flu strains that kill young adults, as was seen in 1918 and is being reported from Mexico. In these cases, a person's healthy immune system may overreact, causing a "cytokine storm" that can cause excessive inflammation in the lungs, leading to death.
"It is almost as though the patient self-destructed," Alexander said.
As scientists unravel the genetic makeup of swine flu strains collected in Mexico, the U.S. and New Zealand, they are relieved to find differences between the 1918 strain and the current strain that suggest a lower potential for severe illness. Some experts suggest the virus may be mutating into a less dangerous form as it spreads.
"It might be losing its steam," said Bellur Prabhakar, professor and head of microbiology and immunology at the University of Illinois at Chicago. "What we're seeing in the United States has us hoping that the pandemic may not be as bad."