The flu is spread every 30-45 years since the 16th century, so we know when to prepare and how to do it. Also, we have learned where it will strike and the containment. Hope this helps! :)
When the body senses foreign substances (called antigens), the immune system works to recognize the antigens and get rid of them. B lymphocytes are triggered to make antibodies (also called immunoglobulins). These proteins lock onto specific antigens.