The first observations of illness and mortality of the Spanish Flu were actually in the US. The origin of the name of the Spanish Flu is due to it being reported in the news most freely and widely in Spain as many other nations were limiting reporting due to being embroiled in WWI.
>>swader+V3
The Wikipedia page cites no theory that places the origin in Spain. It cites theories of origin for the US, France, China and Europe in general.