Washington, Mar 17 (IANS): About a third of wastewater sampling sites across the US have shown an uptick in Covid-19 cases across the country, according to latest data from the US Centers for Disease Control and Prevention (CDC).

In the 15-day period running from February 24 to March 10, 145 wastewater sampling sites out of 401 active sites revealed an increase of 10 per cent or more in coronavirus wastewater levels, Xinhua news agency reported citing the CDC update.

Sixty-two of those sites showed an increase of 1,000 per cent or more, while 48 increased anywhere from 100 per cent to 999 percent, the data showed.

According to a Bloomberg report on Monday, a 10-day detection of Covid-19 at the sampling sites from March 1 to March 10 was much higher than the period running from February 1-10, although during that period fewer sites were available for testing.

Examining wastewater through household and building toilets, showers and sinks, as well as non-household sources like rain and industrial uses, does not identify confirmed cases but provides an early warning about the rise of Covid-19, according to The Hill news outlet.

Meanwhile, the CDC has also confirmed that BA.2 sub-lineage of the Omicron variant now makes up nearly a quarter of new Covid-19 infections in the US.

This data is up from around 1 in 10 new cases just a week prior.

The BA.2 variant is spreading fast in the country, with infections nearly doubling every week, according to CDC data.

BA.2 accounted for only 1 per cent of new cases in the week ending February 5, rising to 2.2 per cent in the week ending February 12, and 4.1 per cent in the week ending February 19, and 7.1 per cent in the week ending February 26, CDC data showed.

The variant was responsible for 23.1 per cent of the cases in the country in the week ending March 12, up from 13.7 per cent in the previous week ending March 5, according to the CDC estimates.

BA.2's prevalence is the highest in the northeast of the country, CDC data showed. In the region spanning New York and New Jersey, the agency estimated 39 per cent of circulating viruses were BA.2. In New England, prevalence of BA.2 was at 38.6 per cent.

Since January, Omicron has made up virtually all new infections in the US.

Early studies showed that BA.2 may be up to 30 per cent more transmissible than the original Omicron. But so far it does not appear to cause more severe diseases.

Health experts are keeping close watch on the variant, urging the public to remain cautious and not let down guard against Covid-19.

As of Thursday morning, the US continued to be the worst-hit country with the world's highest number of Covid cases and deaths at 79,631,708 and 968,329, respectively.