WASHINGTON (BLOOMBERG) - President Donald Trump and his top advisers want global markets and the American public to believe that the coronavirus poses little risk to the US.

But the US Centres for Disease Control and Prevention is saying just the opposite - warning on Tuesday (Feb 25) that the virus's spread in America is inevitable and could bring significant disruption to the world's largest economy.

So far, the markets are siding with the CDC's experts. US stocks hit a 12-week low following the CDC warning, with losses on the S&P 500 totalling 7.6 per cent over four days.

"The American people deserve some straight answers on the coronavirus and I'm not getting them from you," Republican Senator John Kennedy of Louisiana told acting Homeland Security Secretary Chad Wolf at a hearing on Tuesday.

The mixed messages from top US officials illustrated the balance that Trump and his advisers are trying to strike: Demonstrating that they have control over the situation while avoiding any move that spurs a panic and subsequent stock market sell-off as the re-election campaign heats up.

Mr Trump will arrive in Washington early on Wednesday morning with growing questions about the administration's handling of coronavirus.

His Health and Human Services secretary, Mr Alex Azar, will face a second day of scrutiny over the government's response during a Senate hearing on Wednesday on his agency's budget.

Earlier Tuesday, as he concluded a two-day trip to India, Mr Trump told reporters that the disease was "well under control" in the US.

His top economic adviser, Mr Larry Kudlow, declared at the White House later in the day that "we have contained this virus".

But they were contradicted by public health professionals at the CDC.

"We expect we will see community spread in this country," said Dr Nancy Messonnier, director of the CDC's National Centre for Immunisation and Respiratory Diseases.

"It is not a matter of if, but a question of when, this will exactly happen," she said.

The benchmark S&P 500 index extended its losses for a fourth straight day, the longest such streak since Aug 5, falling more than 3 per cent on Tuesday.

Compounding investors' worries about the US government's preparedness, the World Health Organisation reported on Tuesday that the number of global infections exceeded 80,000, up 900 in a day, and that cases were reported in four additional countries - Afghanistan, Bahrain, Iraq and Oman.

There have only been 60 Americans infected so far, according to the CDC, and none have died.

Nevertheless, there is deep concern on Capitol Hill that the government is unprepared for a domestic outbreak.

Some lawmakers have pushed Mr Trump for a more aggressive response, including broader restrictions on travel from countries with outbreaks, but there are worries within the White House about the impact on the economy - and by extension, the president's re-election campaign.

A test for the virus developed in part by the CDC and shared with states has produced inconclusive results, limiting the ability of local health departments to detect the disease and raise alarm if it's silently spreading through US communities. That's crucially important, given that mild cases can resemble the flu.

"I am frustrated that we have had issues with the test," Dr Messonnier said.

The agency is working on a modified test kit it hopes to send out to state and local health departments as soon as possible. Twelve states and localities are now able to perform testing on their own, she said.

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Through Feb 23, the CDC conducted 2,620 coronavirus tests on 1,007 patients. While it has no backlog, completing the test involves sending a sample back to the agency, potentially delaying results.

The US also has far fewer protective masks than it would need in the case of a major coronavirus outbreak, Mr Alex Azar told lawmakers.

There are about 30 million stockpiled N95 masks that can block infective particles, Mr Azar said, but the country would need as many as 300 million for health workers in an outbreak.

MORE MONEY

The Trump administration asked Congress on Monday to provide US$2.5 billion (S$3.50 billion) to help fight the looming outbreak, money that would be used to help expand disease surveillance, bolster state and local health agencies, fund work on vaccines and drug treatments and help fortify the strategic national stockpile with protective gear including masks and respirators.

About half of the US$2.5 billion would come from reallocated funds, including US$535 million for efforts to combat Ebola, according to a person familiar with the matter.

Democrats and some Republicans said the White House's request was not enough.

Even some close Trump allies expressed frustration with the government's preparations and public statements.

Asked to comment on Mr Kudlow's assertion that the virus is contained in the US, Senator Roy Blunt, a Missouri Republican, demurred.

"I can't comment on what the White House has been saying on this, because the people who work for the White House are not saying that," he said.

Mr Kennedy complained that US officials couldn't consistently answer even basic questions about the virus. In a hearing on Tuesday morning, he asked Mr Wolf about the disease's mortality rate.

"Worldwide I believe it's under 2 per cent," Mr Wolf said, saying he'd provide an exact figure from the CDC. "It changes daily. It's under 2 per cent, it was as high as 3."

Asked the mortality rate of influenza, Mr Wolf said, "it's also right around that percentage as well."

"You sure of that?" Mr Kennedy said. While seasonal flu kills as many as tens of thousands of Americans each year, its mortality rate is less than 0.5 per cent this year, in part thanks to broad vaccination.

'RADICAL TRANSPARENCY'

After the hearing, Mr Kennedy said that officials "need to speak straight up to the American people, and when they don't know an answer, they need to say we don't know the answer to that but we're working on it".

A Homeland Security Department spokeswoman said that Mr Kennedy should have directed his questions about the virus's mortality to health care officials, not Mr Wolf.

Mr Azar said that the administration is "trying to engage in radical transparency with the American public as we go through this".

"Each of those messages is accurate, but addresses a particular aspect of what we're talking about," he said.

"Abroad, this is spreading quite rapidly. In the United States, thanks to the President and this team's aggressive containment efforts, this disease is contained."

Mr Trump, tweeting grievances about the prosecution of his friend Roger Stone as he flew back to Washington, will return to a city consumed by concerns about the coronavirus and his government's preparations.

His message to Americans, so far, has been that even if they get sick, the virus is unlikely to kill them.

"There's a very good chance you're not going to die," from a coronavirus infection, Mr Trump said in India.

Of the 60 Americans who have become infected so far, 36 were on a cruise ship in Japan that was the site of one of the largest outbreaks outside China. None have died.

"We think they'll be in very good shape very, very soon," Mr Trump said.

Mr Blunt, the Missouri Republican, took a darker and more global view. After a classified briefing from US officials at the Capitol, Mr Blunt said: "It would be true that most of them are getting better."

But he added: "They're not all getting better. The ones that died aren't getting better."