Omg im really scared! im going on an awesome feild trip , and i really dont want swine flu! what do i do?

im going on an awesome school field trip on tuesday, and my brother said hes feeling sick!!! his best friend just had swine flu and he was at our house the other day! now im afraid it spread to my brother, and i REALLY REALLY dont want to stay home and miss the field trip too washington d.c.! what do i do to prevent me from getting infected?!