The US Center for Disease Control and Prevention (CDC) has warned that the coronavirus outbreak could cause “severe disruption” to the lives of ordinary Americans, and urged families and communities to start making preparations.

The extent of the spread of the virus in the US is uncertain, as the CDC stopped the distribution of coronavirus testing kits after they were found to be flawed. Working testing kits are now available in only a handful of states, and it is not clear when new kits will be ready.

Donald Trump told journalists in India on Tuesday that coronavirus is “very well under control in our country” and “is going to go away”.

Q&A How can I protect myself and others from the coronavirus outbreak? Show The World Health Organization is recommending that people take simple precautions to reduce exposure to and transmission of the coronavirus, for which there is no specific cure or vaccine. The UN agency advises people to: Frequently wash their hands with an alcohol-based hand rub or warm water and soap

Cover their mouth and nose with a flexed elbow or tissue when sneezing or coughing

Avoid close contact with anyone who has a fever or cough

Seek early medical help if they have a fever, cough and difficulty breathing, and share their travel history with healthcare providers

Advice about face masks varies. Wearing them while out and about may offer some protection against both spreading and catching the virus via coughs and sneezes, but it is not a cast-iron guarantee of protection Many countries are now enforcing or recommending curfews or lockdowns. Check with your local authorities for up-to-date information about the situation in your area. In the UK, NHS advice is that anyone with symptoms should stay at home for at least 7 days. If you live with other people, they should stay at home for at least 14 days, to avoid spreading the infection outside the home.

However, the head of immunization at the CDC, Nancy Messonnier, said that disruption to everyday life may be severe as the virus spreads among local communities.

“As more and more countries experience community spread, successful containment at our borders becomes harder and harder,” Messonnier said in a telephone press briefing.

“Ultimately, we expect we will see community spread in this country. It’s not so much a question of if this will happen any more, but rather more exactly when this will happen, and how many people in this country will have severe illness.”

In the absence of a vaccine or medicines, other methods would be needed to contain the spread of the disease, including possible school closures, and telecommuting where possible instead of travelling to workplaces.

“I understand this whole situation may seem overwhelming, and that disruption to everyday life may be severe. But these are things that people need to start thinking about now,” Messonier said. “I had a conversation with my family over breakfast this morning, and I told my children that – while I didn’t think they were at risk – right now, we as a family, need to be preparing for significant disruption of our lives.”

The CDC acknowledged that the test kits it began distributing to state authorities earlier this month have been found to be faulty. The agency said in a statement that “performance issues were identified related to a problem in the manufacturing of one of the reagents which led to laboratories not being able to verify the test performance”.

Messonier said that 12 “states and localities” had working test kits, but according to independent health experts, that overall number includes only five states.

“I am frustrated like I know many of you are that we have had issues with our kit, and I want to assure you that we are working to modify the kit and hope to hand out a new version to state or local jurisdictions soon,” she said, adding: “We are working as fast as we can.”

Jeremy Konyndyk, who led the Obama administration’s response to the Ebola outbreak in 2014, said it was unclear why the US was lagging behind the rest of the world on testing.

“It is puzzling to me that the government has been unable so far to resolve that problem, at a time when most other countries that are facing the disease have been able to do testing at a much larger scale,” Konyndyk said. “We have a lot of people in the government working very, very, very hard on this, but we do not have the kind of fully mobilized US government response that we need.”

He also expressed alarm at the gulf between the Trump reassurances and the situation being presented by the president’s own officials.

“The president’s overarching priority here seems to be much more about keeping the markets calm than taking every measure to keep Americans safe, and that worries me,” Konyndyk said. “And it also makes me wonder if they are leaving some [preventive] options on the table for fear of spooking the markets.”

Stock prices plunged at new reports showing the the worldwide spread of the virus. The Dow Jones industrial average dropped 877 points or 3.1% on Tuesday.

So far, 14 coronavirus cases have been identified in the US, including 12 travellers returning from abroad, and two patients who had contact with those returning travellers.

In addition, 40 Americans who tested positive on the Diamond Princess cruise ship have been repatriated, and three repatriated from China.

“The coming week is going to be a very telling time in this outbreak,” Saskia Popescu, an epidemiologist at George Mason University, said. “There’s a lot of concern around the limited testing that’s getting done in the United States right now.”

Popescu said there was also a serious shortage of personal protective equipment, such as face masks .

The health and human services secretary, Alex Azar, asked for $2.5bn in emergency funding. He said the country currently has a stockpile of 30m surgical masks, but his department estimated that 10 times that number could be needed.

Senators questioned the administration’s preparedness and pointed out that Azar himself had proposed drastic budget cuts. The Trump administration has also dismantled the office in the national security council that was set up in the wake of the Ebola virus scare to coordinate government responses to pandemics.

After receiving a classified Senate briefing on the coronavirus, Democrat Richard Blumenthal tweeted that it should have been made public.

“They would be as appalled and astonished as I am by the inadequacy of preparedness and prevention,” Blumenthal said.