U.S. Attorney John P. Kacavas said his office interviewed employees at Exeter who said they had seen Kwiatkowski acting strangely, one time sweating profusely and with bloodshot eyes.

"One of them described him as unfit to provide medical care and his supervisor sent him home," Kacavas said. "He provided a plausible explanation for his condition, which was that he had been crying his eyes out because his aunt had died and he was an emotional wreck."

According to state, county and hospital officials, he worked as a radiology technician and medical technician in cardiac catheterization labs in the following locations:

-- Oakwood Annapolis Hospital in Wayne, Michigan, January to September 2007;

-- Saint Francis Hospital, Poughkeepsie, New York, November 2007 to February 2008;

-- UPMC Presbyterian, Pittsburgh, March 2008 to May 2008;

-- Baltimore Veterans Affairs Medical Center, May 2008 to November 2008;

-- Southern Maryland Hospital, Clinton, Maryland, December 2008 to February 2009;

-- Maryvale Hospital, Phoenix, March to June 2009;

-- Johns Hopkins Hospital, Baltimore, July 2009 to January 2010;

-- Maryland General Hospital, Baltimore, January 2010 to March 2010;

-- Arizona Heart Hospital, Phoenix, March 2010 to April 2010;

-- Temple University Hospital, Philadelphia, April 2010;

-- Hays Medical Center, Hays, Kansas, May 2010 to September 2010;

-- Houston Medical Center, Warner Robins, Georgia, October 2010 to March 2011.

-- Exeter Hospital, Exeter, New Hampshire, April 2011 to July 2012.

Institutions say they are calling former patients and offering free testing, and that the U.S. Centers for Disease Control and Prevention is helping state health officers and hospitals tackle the problem.

Kwiatkowski was arrested earlier this month after police found him in a Massachusetts hotel room "in an intoxicated state" and took him to a hospital, the affidavit states. He is now being held in the Strafford County, New Hampshire, jail. He could face more than 20 years in prison if convicted.

Kwiatkowski appeared in New Hampshire federal court Tuesday and waived his right to a detention hearing. Kacavas said it is possible more charges could be filed.

Bjorn Lange, a public defender representing Kwiatkowski, told CNN Friday he would have no comment.