As few as 1,000 SARS-CoV2 viral particles are needed for a COVID-19 infection to take hold. That's based on the MERS and SARS outbreaks. A single breath releases 50 to 5,000 droplets. If a person coughs or sneezes, 200,000,000 viral particles go everywhere. University of Massachusetts Dartmouth Professor Erin Bromage searched...