Narrative:

We were cruising at FL370 and knew of a 747-800 freighter converging off our right at a higher altitude. [Center] told us about the 747 and even elaborated that it was a 'brand new' airplane. My first officer and I mentioned to each other the implications of being behind the 747 and I had read once about its new wing design and wondered what kind of wake the plane might cause. The 747 soon was out of sight and we elected to climb to FL380 for a better ride. First officer was flying and somewhere around FL375 we encountered the most violent wake turbulence I've ever experienced. I took control of our aircraft and for a brief moment could not stop the roll to the right. I lowered the nose because the airspeed had decrease; I had the stall bar in view (HUD) as well. I elected to descend quickly and told [center] that we were in 'that guys wake' and they said no problem; descend to whatever we needed and also to offset to the upwind side of our route.once we regained control of our aircraft; we checked on the flight attendants and passengers. Two or three passengers had bumped their heads and all three of our flight attendants were momentarily airborne/off their feet. We made sure a medical divert was not needed and continued to [destination]. We called dispatch and informed them that the aircraft would be written up for a severe turbulence encounter. I communicated with the flight attendants and made sure no one needed paramedics upon arrival.not sure I have an answer. Some of these bigger and newer aircraft (747-800 or whatever it's called and the A380) I really don't want to be anywhere behind them. Incidentally; [center] said we were 13 miles behind this aircraft when this event took place. It was eye-opening to say the least.

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Original NASA ASRS Text

Title: A B737-700 encountered severe wake turbulence in trail of B747-800 that was almost 14 NM ahead of them; resulting in strong roll to the right and loss of altitude.

Narrative: We were cruising at FL370 and knew of a 747-800 freighter converging off our right at a higher altitude. [Center] told us about the 747 and even elaborated that it was a 'brand new' airplane. My First Officer and I mentioned to each other the implications of being behind the 747 and I had read once about its new wing design and wondered what kind of wake the plane might cause. The 747 soon was out of sight and we elected to climb to FL380 for a better ride. First Officer was flying and somewhere around FL375 we encountered the most violent wake turbulence I've ever experienced. I took control of our aircraft and for a brief moment could not stop the roll to the right. I lowered the nose because the airspeed had decrease; I had the stall bar in view (HUD) as well. I elected to descend quickly and told [Center] that we were in 'that guys wake' and they said no problem; descend to whatever we needed and also to offset to the upwind side of our route.Once we regained control of our aircraft; we checked on the flight attendants and passengers. Two or three passengers had bumped their heads and all three of our flight attendants were momentarily airborne/off their feet. We made sure a medical divert was not needed and continued to [destination]. We called Dispatch and informed them that the aircraft would be written up for a severe turbulence encounter. I communicated with the flight attendants and made sure no one needed paramedics upon arrival.Not sure I have an answer. Some of these bigger and newer aircraft (747-800 or whatever it's called and the A380) I really don't want to be anywhere behind them. Incidentally; [Center] said we were 13 miles behind this aircraft when this event took place. It was eye-opening to say the least.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.