<s>[INST] What is fever of unknown origin (FUO)? [/INST]  Fever of unknown origin (FUO) was defined as ‘fever with a temperature of more 101°F on several occasions, lasting more than 3 weeks, which includes a hospital stay of more than 1 week with a failure to diagnose the cause’ by Petersdorf and Beeson in 1961. Source: MED INDIA. Link: https://www.medindia.net/symptoms/fever-faqs.htm. Field: Infectious Disease. Disease: Fever </s>