Wow that's a prety big spike in fatalities.
Something like that happened here in the states back in the 90's?? we were geting more people to wear helmets but the number of injuries per mile went up. You do expect the # of injuries to go up with more people riding but what no one expected was the rate of injury also went up. sorry I don't have a reference source but this sort of stuck in my mind at the time...
Still nominal of 2-3 to 19/1.5 (because of 6 week period) or 13 fatalities in a month is shocking.