COVID Data Tracker Weekly Review

Monitoring Variants

Viruses constantly change through mutation, and sometimes these mutations result in new variants of the virus. Numerous variants of SARS-CoV-2, the virus that causes COVID-19, have been tracked in the United States and globally during this pandemic. The Omicron variant, like other variants, is made up of a number of lineages and sublineages. These lineages are often very similar to each other, but there can be differences that affect the behavior of the virus.

CDC is closely tracking a wide range of Omicron sublineages, including three drawing recent attention. BQ.1 and BQ.1.1 are offshoots—grandchildren, if you will—of the BA.5 that’s been dominant for months. CDC data show that they seem to be spreading relatively quickly so far, but they’re still a small proportion of overall variants. CDC is also keeping a close eye on a sublineage called XBB based on international reports, although it’s still very rare in the United States.

Sometimes new variants emerge and disappear. Other times, they persist and continue to circulate in communities. As the virus spreads, it has new opportunities to change in ways that can make emerging variants more difficult to stop because the effectiveness of vaccinations or treatments may be reduced. We can monitor mutations from one variant to another and monitor the impact of these changes by comparing differences in real-world characteristics, such as effectiveness of vaccines or treatments. By studying each variant and understanding these differences, scientists can monitor whether a new variant might be more dangerous.

CDC is using multiple surveillance systems to monitor variants in the United States. Data from each system plays an important role in helping us understand the emergence of new variants, whether they’re entering the United States and spreading, and which variants are most prevalent within communities. On October 20, 2022, COVID Data Tracker added a new Variant Summary page, which summarizes three systems that are being used to monitor variants. For more information on these systems, see A Closer Look.