Sacha Pfeiffer, WBUR, June 2, 2009 Boston - With all the reminders lately to wash your hands to prevent the spread of flu, you might feel like you’re back in grade school. But it can be so hard to get people to follow proper hand hygiene that even many doctors and nurses don’t do it correctly. That contributes to 1.7 million hospital-acquired infections each year. So several Boston hospitals have launched hand-washing campaigns, including some that involve rap music videos and undercover surveillance. Everywhere you look at Massachusetts General Hospital, there seems to be a dispenser of hand sanitizer. They’re next to ATM machines. They’re in elevator lobbies. They’re inside and outside patient rooms. ... Rapping