Greg - I think that malaria and yellow fever were quite similar diseases caught in similar circumstances. We know they are different dieases now because we're better at diagnosis. Of course, nobody knew in those days that it was those pesky mosquitos that were behind it all. The term malaria just means 'bad air', the kind you get near fetid swamps. Yellow fever was known as vomito negro or the black spit and that was the main difference in symptoms. Both diseases may be known locally as 'swamp fever'. All people knew was that swamps were not healthy places. In 1809 'Walcheren fever' (probably malaria and typhus with a bit of dysentry and typhoid thrown in) killed 4000 men and put many more on the sick list for months. So be careful with all that swamp music you play!