Washington, Mar 25 (IANS): The US Centers for Disease Control and Prevention (CDC) has expressed concerns over a surge in the number of new Covid-19 cases as more states were easing restrictions and also an increase in domestic travel.

During a virtual White House Covid-19 Response Team briefing on Wednesday, CDC Director Rochelle Walensky said the US witnessed the seven-day average of new daily cases climb to 53,800 over the past week, while the two-week average has wavered between 50,000 to 60,000 cases per day, Xinhua news agency reported.

Walensky warned that US states are seeing an increasing number of new cases attributed to variant strains of the virus, particularly in California, currently the worst-hit, where a new variant accounts for 52 per cent of fresh infections.

The US is at a critical point in the pandemic and is worried if the nation does not take the correct actions, it is headed for an "avoidable surge", she added.

In yet another grim milestone, the coronavirus caseload in the US has surpassed the 30 million mark, as the pandemic still rages in the world's worst-hit country, according to the Johns Hopkins University.

In its latest update on Thursday morning, the University's Center for Systems Science and Engineering (CSSE) revealed that the country's overall number of cases and fatalities stood at 30,009,386 and 545,237, respectively.

The US remains the worst-hit nation making up more than 24 per cent of the global caseload and nearly 20 per cent of the overall fatatlities.