THE confirmed number of Covid-19 cases in the US has reached 5 million, according to the tally kept by Johns Hopkins University.

The number is by far the highest of any country in the world but health officials believe that for every reported case, there are roughly 10 times as many people infected, given the limits on testing and the mild infections that have gone unreported or unrecognised.

The bleak milestone was reached as new cases in the US stand at about 54,000-a-day.

While that is down from a peak of more than 70,000 in the second half of July, cases are rising in nearly 20 states, and deaths are climbing in most.

READ MORE: Coronavirus: 48 new cases recorded in Scotland as positive tests near 19,000

Many Americans have resisted wearing face masks and social distancing.

The United States' failure to contain the spread of coronavirus has been met with astonishment and alarm in Europe.

Italians were unprepared when the outbreak exploded in February, and the country still has one of the world's highest official death tolls at 35,000.

However after a strict nationwide, 10-week lockdown, vigilant tracing of new clusters and general acceptance of mask mandates and social distancing, Italy has become a model of virus containment.

Much of the incredulity in Europe stems from the fact that the US had the benefit of time, European experience and medical know-how to treat the virus that the continent itself did not have when the outbreak started there. 

Italian health minister Roberto Speranza has expressed amazement at President Donald Trump's virus response.

After the US president finally donned a mask last month, Speranza said: "I'm not surprised by Trump's behaviour now; I'm profoundly surprised by his behaviour before."

More than 162,000 have died from the virus in the US and European nations have barred American tourists and visitors from other countries with growing cases from freely travelling to the bloc.

France and Germany are now imposing tests on arrival for travellers from "at risk" countries, including the US.