... the negative karma that contains the factor of illness.

It is true that we can overcome various illnesses by chanting Nam Myoho Renge Kyo to the Gohonzon and there are many believers who have recovered by chanting the mantra. Of course, we need to see a doctor and receive appropriate treatment from him but chanting the mantra is necessary to change the negative karma that contains the factor of illness.

Is 'factor' OK? I think 'cause' or 'causes' would be better? Am I right?

Thanks.