A new Omicron variant, BA.2.12.1, has taken over in Massachusetts. Here’s what you need to know.
BA.2.12.1, first identified in New York, now accounts for 70 percent of new cases in Massachusetts, according to the Broad Institute of MIT and Harvard.
The virus that causes COVID-19 didn’t change much in the early days of the pandemic. Then the number of mutations started increasing, and scientists began using an alphabet soup of letters and numbers to distinguish them.