Some of these small parasites have been mutating and are now resistant to many over-the-counter medications.
President Barack Obama on Monday nominated Chuck Hagel as his next secretary of defense and John Brennan as the next head of the CIA.
Both nominations are likely to be controversial. Hagel, a former senator, has been criticized by fellow Republicans over his positions on Israel and Iran.
Brennan has faced questions about his connection to controversial interrogation tactics used during the Bush administration.
Brennan, who was the CIA’s deputy executive director under President Bush, is now President Obama’s counterterrorism adviser.