My husband is having flu like symptoms. He had a flu shot one week ago. Currently Temp 100.2 headache, nausea, lethargy. He had a work up to rule out gallbladder issues on 10-7-18 after severe abdominal pain and vomiting. No appetite. He is having EGD tomorrow and doesn't want to take anything for pain until after the EGD. Any ideas about what his problem could be. Age 67, white male, active. No health issues.