Help! My father who is almost 73 was prescribed Levaquin for a ...

Help! My father who is almost 73 was prescribed Levaquin for a possible sinus infection. He took the last dose of a ten day prescription on April 26 (Today is May 17} Almost a month later he is suffering from many flu-like symptoms(fever, chills, weakness, loss of appetite, and etc. As well as the typical tendon pain and according to the Dr. - Bronchitis) My question is how typical is it to have the flu, bronchitis symptoms 3 weeks later? Any suggestions would be greatly appreciated!