If 5m people annually from outside Brazil are already travelling to the region and being exposed to the virus, an additional 500,000 is not going to make much of an impact is it if risk of the virus spreading is already a significant risk.
Also if the risk of transmission is mainly via insects, I am not sure of the relevance of it being a compact event.
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because most of the time you don't have a huge amount of people crammed into one event, one event that is held in a city, that despite attempts to control the infection is still spreading uncontrolled.
the more dense it is the easier it is for mosquitos to pass it on and thrive.
so yes it's likely to make a large difference. compared to vastly more spread out tourism, of which many will be in much lower risk areas.
 
	 
  
 
		 
 
		 
 
		 
 
		 
 
		
 
 
		 
 
		
