Susceptibility to influenza A (H1N1) infection is significantly increased by exposure to low levels of arsenic commonly encountered in contaminated well water. This is the conclusion of researchers who studied the effects of low levels of arsenic in the drinking water of mice. The initial immune response of these mice to influenza A (H1N1) was quite feeble and when the response was made it was too robust and too late. "There was a massive infiltration of immune cells to the lungs and a massive inflammatory response, which led to bleeding and damage in the lung," said Dr. Joshua Hamilton, an author of the study. Morbidity over the course of the infection was significantly higher for the arsenic-exposed mice than for the normal mice. The U.S. Environmental Protection Agency considers 10 parts per billion (ppb) arsenic in drinking water "safe," yet concentrations of 100 ppb and higher are commonly found in well water in regions where arsenic is geologically abundant, including upper New England (Massachusetts, New Hampshire, Maine), Florida, and large parts of the Upper Midwest, the Southwest, and the Rocky Mountains. Respiratory infections with influenza A virus are a worldwide health concern and are responsible for 36,000 deaths annually. The recent outbreak of the influenza A H1N1 substrain ("swine flu"), which is the same virus used in this study, has, to date, killed 72 people in Mexico and 6 in the United States. "One thing that did strike us, when we heard about the recent H1N1 outbreak, is Mexico has large areas of very high arsenic in their well water, including the areas where the flu first cropped up. We don't know that the Mexicans who got the flu were drinking high levels of arsenic, but it's an intriguing notion that this may have contributed," Dr. Hamilton said.
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