My uncle (Age 68) has been on High BP medication for last 15+ yrs. He recently had chest, stomach and urine infection in August and was admitted to a nursinghome with high fever, sudden hypoxia, and 1 episode of heart failure. At nursinghome, chest infection impression was stated 'like bronchitis', and stomach infection was stated as 'enteric fever'. During release after 8 days, doctor said that people on prolonged High BP meds were prone to infections at old age. We followed up with same doctor each month, conducting almost all advised routine tests each time, and every time the values improved and normalized within respective ranges. However, the fever has started recurring since last Saturday, around 100-101 at daytime and 101-102 at night. There are presently no other symptoms except fever. Current Urine tests, XRay, USG & Echo are all OK, incl. Blood work, except Hb is 10.5, total RBC 3.88, ESR 45, CRP 59. Except high BP, he never had any health issues. What could be the problem?