The total number of PML cases in persons using Tysabri for MS and Crohn's disease was 517 as of December 3, 2014. Three of the 517 cases have been persons with Crohn's disease.
This means an incidence of PML of 3.78 per 1,000, and 23% have died. 77% are alive with varying levels of disability.
As of 9/30/14, a total of 132,600 patients worldwide have received Tysabri in a post-marketing setting.
This information is from the chefarztfrau Website.
Since the number of people on Tysabri has been steadily rising and the number of PML cases has shown a slight decline recently, it seems likely that the measures that have been taken towards better early detection have had some effect.
The total number of PML cases recorded in 2011 was 103, in 2012--119, in 2013--106, and in 2014--94.