The US has surpassed 40 million coronavirus cases since the start of the pandemic, according to Johns Hopkins University.

The Maryland-based school registered 40,096,188 cases and 649,438 deaths as of Tuesday.

The US has been of late grappling with the delta variant which accounts for most cases in recent weeks and now a new variant, mu, is spreading across the US.

The variant, first discovered in Colombia in January, has been detected in 49 US states, according to multiple outlets.

Last week, the World Health Organization (WHO) said it was monitoring the new variant, which was added to the WHO’s list of variants "of interest" in late August.

According to the US' leading infectious disease expert, Dr. Antony Fauci, the mu variant shows mutations that "indicate that it might evade the protection from certain antibodies."

He said it was "not an immediate threat."

The White House announced that President Joe Biden will deliver a speech on Thursday about his plans to stop the spread of the delta variant and boost COVID-19 vaccinations.

So far, more than half of the US population or nearly 176 million people have received a COVID-19 vaccine as part of the effort to fight the virus./aa