More transmissions mean more chances at mutations. This isn't just true for humans, but also the animal carriers of pathogens who now live closer together. Mob

More transmissions mean more chances at mutations. This isn't just true for humans, but also the animal carriers of pathogens who now live closer together. Mobility is also a factor in transmission. MERS was fatal enough to burn itself out, but in a less mobile world it would've burned out even faster.