I'll grant you that! But in the 50's there were no biological weapons programs by foreign countries, nor the threat of such.
And besides, Jim, there wasn't as much travel between countries and continents as there is today.
I'd love to have lived as an adult in the '50s BTW.
... we *still* got Cholera freom across 'the big pond' in 1932 ...
As to travel - what was the total figure for emigration *into* the United States (and many of these emmigrants brought with them al manner of contagion) over the course of our history?