Thanks to Smt Andal Perumal for the share!
There is no question that these namas of bagavan has lot of powers to cure all diseases. I read one incident (long back) where a devotee was asked to chant Vishnu Sahasranamam by Periyava as the devotee did not learn veda etc and felt bad that he missed the bus. With Periyava’s kind direction, he started chanting Vishnu Sahasranamam daily. At one point it became a penance – he did nothing but this with utmost sincerity. In his death-bed, Sri Mahavishnu Himself gave darshan for this devotee before he left this world! This was witnessed by all the relatives who were at his last hours.
Aum Nama Narayanaya!