There have also been rare documented cases of humans passing the infection to other humans.

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From December 2005 to February 2009, 12 cases of human infection with swine flu were documented.

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Since 1991, only three cases of dental infection in patients have been documented -- two with hepatitis B and one with HIV, according to the CDC.

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Since 1991, only three cases of dental infection in patients have been documented -- two with hepatitis B and one with HIV, according to the Centers for Disease Control and Prevention.

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The findings, reported Sunday by researchers, mark only the second documented case of a patient being cured of infection with the human immune-deficiency virus.

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More than 70 countries have reported cases of human infection with the virus, and more than 70, 000 cases have been documented worldwide, according to the WHO.

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