Yes you DO, dude. Ever been overseas in Africa? I have. You cram too many people together and mix in bad sanitation and you DO get outbreaks of Ebola and such.
Know what invention saved more human lives than any other single thing in the entire histpry of mankind? Sanitation. Sewers. Before that, cities were breeeding grounds for every kind of sickness imaginable, and it did not stop until people discoivered basic rules like "thou shalt not walk in steams of your own waste- thou shalt route it underground and not touch it". "Resources" have nothing whatsoever to do with it.
The only thing stopping something like Ebola in an outlying areas is that it's so lethal that it drops you before you can walk the 5 miles to the next villiage. Now put that Ebola victim on a crowded subway- he could infect 5,000 people before he vomits up blood and gets quarantined. Then those 5,000 infect 100 others just getting groceries or going to the movies or riding on the bus... Do the math. THAT's wha tthis guy was saying.., that we're setting ourselves up for the next nmutated virus or bacteria and that people that routinely jam themselves into crowded subway cars with 600 people will be the first ones to drop.