I had it. 52 yrs old at the time. Started feeling bad so went to doc (A Harvard guy who loved the country life). He took one look at me and said you have it. Took a test and sent me for tamiflu, but said it won't really help much but may lessen the hit. He said you will have a fever and feel like your head is coming off for 3-4 days. It will take 10-14 days to feel just barely good enough to go to work In an office.. He was 100% correct. Never had a headache like that. Went from throwing up to passing out in that order every 10-15 minutes for 3 days. It sucked - I lived - period.