US tracking of virus variants has improved after slow start

  • FILE - James Robson, a biomedical engineering graduate student, holds a swab and specimen vial in the new COVID-19, on-campus testing lab, Thursday, July 23, 2020, at Boston University in Boston. The United States has improved its surveillance system for tracking new coronavirus variants such as omicron, boosting its capacity by tens of thousands of samples since early 2021. (AP Photo/Charles Krupa, File)

After a slow start, the United States has improved its surveillance system for tracking new coronavirus variants such as omicron, boosting its capacity by tens of thousands of samples per week since early this year.