Influenza pneumonia results when a flu infection spreads to alveolar air sacs deep within the lungs. Normally, a flu infection does not progress that far into the lower respiratory tract, but when it does, the results can be deadly.
"If infection is severe enough, and the immune response is potent enough, you get injury to these cells and are no longer able to get sufficient oxygen exchange. As a result of the infection of the cells, you can develop lethal pneumonia and die," said Thomas J. Braciale, researcher from University of Virginia in the US.
The findings showed that early administration of the two asthma drugs -- Accolate and Singulair -- could prevent the infection of the alveolar cells deep in the lower respiratory tract.
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Once influenza spreads deep into the lungs, the body's own immune response can prove harmful, resulting in severe damage to the alveolar air sacs, the researchers said.
The alveolar epithelial cells are typically protected from influenza infection by immune cells called alveolar macrophages.
In some instances, however, the flu virus can prevent the macrophages from carrying out their protective function, allowing the epithelial cells to become vulnerable to infection.
"It's not as though they lack alveolar macrophages, it's just that their alveolar macrophages don't work right when they get exposed to the flu," Braciale said.
"And those are the types of patients, who potentially would eventually go to the intensive care unit, that we think could be treated early in infection with Accolate or Singulair to prevent infection of these epithelial cells and prevent lethal infection," he added.