The COVID variant BA.2 has accounted for 11.6 percent of new U.S. COVID cases over the past week up to March 5th, projections from the Centers for Disease Control and Prevention (CDC) show.
The new CDC figures mark a notable increase in the proportion of BA.2 in the country. The week prior, BA.2 was estimated to account for around 6.6 percent of new cases and 3.8 percent of new cases in the week before that.
This means the proportion of BA.2 cases in the U.S. is rising week by week. In the most recent data set, other Omicron sub-types made up the remaining 88.4 percent of cases. It should be noted that figures for the past two weeks are estimations.
BA.2 is a sub-type of the COVID Omicron variant and is sometimes referred to informally as “Stealth Omicron” since it is detected differently in tests compared to the globally dominant BA.1 Omicron version.
Worldwide, BA.1 has been the most common Omicron lineage but the proportion of reported BA.2 cases has been increasing relative to it in recent weeks. In some countries such as Denmark, BA.2 has become the dominant lineage.
Much research into BA.2 has been conducted this year so far because of its rapid rise in some parts of the world. Scientists have noted that BA.1 and BA.2 have some distinct genetic differences that could in theory change the way they affect people.
In February, the World Health Organization (WHO) stated that BA.2 appears to be more transmissible than BA.1, for example.
However, data thus far has also shown that BA.2 does not appear to cause more severe illness than BA.1. “Preliminary analysis finds no evidence of a greater risk of hospitalization following infection with BA.2 compared to BA.1,” a report from the U.K.’s Health Security Agency (HSA) stated on February 25th. “These are early estimates which may change as data accrue.”
The HSA report followed a study from Japan suggesting that BA.2 makes hamsters more sick than BA.1, which gained much attention. However, experts noted that results from animal studies are not always relevant to humans.
One key characteristic of BA.2 is its ability to infect individuals who have already had BA.1, meaning people could catch Omicron twice in the space of a couple of months. Though some such cases have been reported, the WHO said on Tuesday that infection with BA.1 “provides substantial protection against reinfection with BA.2” based on initial population-level data.
In any case, while the proportion of BA.2 cases is increasing relative to BA.1 in the U.S., COVID cases in the country in general are declining.
CDC data from March 8 shows that the seven-day moving average of new COVID cases in the country was 40,433 on March 7, compared to 66,869 in the previous week.
Source: www.newsweek.com
