BA.2 is about 30% to 50% more contagious than Omicron. It has been detected in 74 countries and 47 US states.
The US Centers for Disease Control and Prevention estimates that about 4% of Americans with Covid-19 now have infections caused by BA.2, but many other parts of the world have more experience with this variant. It has become dominant in at least 10 other countries: Bangladesh, Brunei, China, Denmark, Guam, India, Montenegro, Nepal, Pakistan and the Philippines, according to World Health Organization's weekly epidemiological report.
But, there's mixed evidence on the severity of BA.2 in the real world. Hospitalizations continue to decline in countries where BA.2 has gained a foothold, like South Africa and the UK. But in Denmark, where BA.2 has become the leading cause of infections, hospitalizations and deaths are rising, according to WHO.