The world's death toll from COVID-19 today topped 2 million, with yesterday marking the deadliest day of the pandemic, with 16,056 fatalities logged, amid reports of collapsing health systems in parts of Brazil and exponential spread in some of its neighbors.Death levels are still soaring in hard-hit parts of Europe, and health officials say human behaviors, including those that occurred over the holiday season, are the main driver of virus surges, though they are worried about the potential impact of new, more transmissible SARS-CoV-2 variants.Experts weigh in on variants, vaccinesThe World Health Organization (WHO) COVID-19 emergency committee met for the sixth time yesterday to discuss the latest developments, including the arrival of