As the United States reported a second death from the novel coronavirus, Washington officials told US citizens to be prepared for an escalation in cases, but also expressed confidence that the virus would be brought under control.

In an interview on Sunday, US Vice-President Mike Pence defended the US administration's handling of the epidemic after rising criticism of the state of the country's preparedness.

Pence made the remarks on CNN's State of the Union, saying that risks from the disease remain low for most US citizens, while promising to make up for testing shortfalls.

"We could have more sad news, but the American people should know the risk to the average American remains low," Pence said.

The assurances came a day after officials confirmed that two men had died in the northwestern state of Washington after becoming infected with the virus.

The first was a man in his 50s, with no known contact with people infected abroad. The second was a man in his 70s. Both had "underlying health issues," according to reports.

The US has had about 80 confirmed coronavirus cases in all, including 47 patients who were repatriated from the cruise ship Diamond Princess in Japan, according to the Centers for Disease Control and Prevention, or CDC.

Genetic analysis suggests the virus had probably been spreading undetected for about six weeks in Washington state, The New York Times reported.

The spread of the virus through communities would be an ominous development that would almost certainly intensify the epidemic in the United States.

When asked on CNN why the US was so far behind other countries in producing testing kits, Pence said more than 15,000 testing kits were released over the weekend, the federal Food and Drug Administration has approved a testing regime, and the government was working with a commercial provider to produce an additional 50,000 kits.

US President Donald Trump put Pence in charge of the response to the virus last week, amid rising complaints that the administration had been slow to prepare for the virus' spread.

Trump himself had been criticized for seeming to low-ball the risk, even as experts from the CDC warned of a looming health emergency.

In defending the administration's response, Pence credited Trump with acting quickly to establish quarantines for US citizens brought back from countries at high risk.

'Don't buy a mask'

Meanwhile, as US citizens take precautions, health officials have been unanimous in saying: Don't buy a mask.

"STOP BUYING MASKS!" US Surgeon General Jerome M. Adams posted on Twitter on Saturday morning.

They aren't effective in preventing people from catching the coronavirus and instead put sick patients and communities at risk if health-care providers can't get them, he said.

US citizens have been rushing to buy masks, which has led to price-gouging and counterfeit products.

Pence said the White House virus group is working to develop a course of action that would prioritize masks for use by "high-risk "health-care professionals, while adding that the US is contracting with 3M to create 35 million more masks each month.

Agencies and Linda Deng in Seattle contributed to this story.