US death toll nears 11,000

• NY governor warns against complacency
• US begins blood tests for immunity: reports
• 90% of Americans ordered to stay home

The governors of New York, New Jersey and Louisiana pointed to tentative signs on Monday that the coronavirus outbreak may be starting to plateau in their states but warned against complacency as the death toll nationwide approached 11,000.

Although coronavirus cases and deaths continued to mount, the governors cited data suggesting the rates of growth and hospitalisations were slowing, possibly signalling a peak was at hand in three US epicentres of the pandemic.

More than 90% of Americans were under statewide stay-at-home orders issued in recent weeks, with South Carolina joining on Monday.

New York Governor Andrew Cuomo said state-wide deaths from Covid-19, the highly contagious respiratory illness caused by the virus, were up 599 from Sunday, on par with an increase of 594 during the previous 24 hours and 630 on Friday.

The state's overall tally of confirmed cases grew by 7% from the previous day to 130,680. But hospitalisations, admissions to intensive care units and the number of patients put on ventilator machines to keep them breathing had all declined, Cuomo said.

"While none of this is good news, the possible flattening of the curve is better than the increases that we have seen," Cuomo told a daily briefing, referring to the trend line formed when infections, deaths and other data are plotted on a graph. "If we are plateauing, we are plateauing at a high level."

For doctors, nurses and emergency personnel in the trenches of the unprecedented public health crisis - many still coping with scarcities of protective garments and other supplies - the pace of their work remained unrelenting.

New York City accounts for two thirds of nearly 4,800 deaths in New York state, which in turn represents about 45% of the nation's total loss of life to date.

In neighbouring New Jersey, the state with the second-highest number of cases and deaths, Governor Phil Murphy cited a 12% day-to-day growth rate in confirmed positive cases on Monday, half the rate from March 30.

The US has begun taking blood samples from across the country to determine the true number of people infected with the coronavirus, using a test that works retrospectively, according to reports.

The new tests are based on serological surveys, which differ from the nasal swabs used to determine if someone currently has the virus, reports AFP.

Instead, they look for whether certain antibodies are present in the blood which shows that the person fought and then recovered from the illness -- even if they never showed symptoms.