He is known to be a political survivor becoming an MLA way back in 1957 but nature seems to be catching up with 94-year-old M Karunanidhi, the former chief minister of Tamil Nadu. The last 24 hours have seen a string of top political leaders visiting his Gopuram residence in Chennai.As per the medical bulletin, the DMK chief is being treated for fever due to urinary tract infection. There has been a decline in his health and he has been kept under constant observation by a team of doctors.