The single most common cause of pyrexia of unknown origin is -
Pyrexia of unknown origin is definedvas a temperature persistently above 38 degree celsius for more than 3 weeks,without diagnosis despite initial investigations during 3 days of inpatient care or after more than two outpatient visits. Specific organisms associated with PUP are tuberculosis( extrapulmonary - most common cause), HIV-1 infection,other viral infections (cytomegalovirus,EBV), fungal infections (Aspergillus spp.,candida spp., dimorphic fungi), infections with fastidious organisms(Baonella spp., Tropheryma whipplei). Reference Harrison20th edition pg 1232
Mycobacterium tuberculosis
Salmonella typhi
Brucella spp
Salmonella paratyphi A
Infection