WHO warns of âvery dangerous periodâ fueled by delta variant By Stephanie Weaver What to know about the delta variant Experts say the delta variant spreads more easily because of mutations that make it better at latching onto cells in our bodies. WASHINGTON - In a press briefing Friday, the head of the WHO said the delta variant is "quickly becoming the dominant strain in many countries," and thus, the world is in a "very dangerous period" of the COVID-19 pandemic. "Delta is spreading in at least 98 countries and is spreading quickly in countries with low and high vaccination coverage," WHO Director-General Dr. Tedros Adhanom Ghebreyesus said.