Coronavirus Live Updates: More Than 1,000 Cases in the U.S.

The U.S. caseload has surpassed 1,000.

As the nation scrambled to understand the scope of the escalating public health crisis, the number of known cases of coronavirus infection in the United States surpassed 1,000 on Tuesday night, signaling that the coronavirus was spreading widely in communities on both coasts and in the center of the country.

America’s first known coronavirus case was announced on Jan. 21 in Washington State. Six weeks later, the number of cases had risen to 70, most of them tied to overseas travel. But since then, new case reports have poured in, first by the dozens, then the hundreds.

A majority of the cases have been in Washington State, California or New York, where everyday life swiftly began to change. Businesses closed. Colleges canceled class. Governors urged people to avoid crowds.

But the virus is now found in every region of the country, including Massachusetts, where dozens of new cases were announced on Tuesday, and South Dakota, where the governor announced the state’s five first cases, including one man who died. The number of states with no reported cases now stands at about a dozen.

Thirty-one deaths across the country have now been linked to the coronavirus. Officials in Sacramento County, Calif., said on Tuesday that a woman in her 90s died after contracting the illness.

Delays in testing set back the U.S. coronavirus response.

In late January, the first confirmed American case of coronavirus had been reported in the Seattle area. But had the man infected anyone else? Was the virus already spreading?

Dr. Helen Y. Chu, an infectious disease expert in Seattle, had a way to monitor the region. As part of a research project into the flu, she and a team of researchers had been collecting nasal swabs for months from residents experiencing symptoms throughout the Puget Sound region.

To repurpose the tests for the coronavirus, they would need the support of state and federal officials. But officials repeatedly rejected her idea, interviews and emails show, even as weeks crawled by and outbreaks emerged outside of China.

By Feb. 25, Dr. Chu and her colleagues could not wait any longer. They began performing coronavirus tests without government approval. What came back confirmed their worst fear: They had a positive test from a local teenager with no recent travel history.

In fact, officials would later discover through testing, the virus had already contributed to the deaths of two people, and it would go on to kill 20 more in the Seattle region over the following days.

Federal and state officials said the flu study could not be repurposed because Dr. Chu’s lab did not have explicit permission from research subjects; the lab was also not certified for clinical work. While acknowledging the ethical questions, Dr. Chu and others argued there should be more flexibility in an emergency.

The failure to tap into the flu study was just one in a series of missed chances by the federal government to ensure more widespread testing during the early days of the outbreak, when greater containment still seemed possible.

Even now, after weeks of mounting frustration toward federal agencies over flawed test kits and burdensome rules, states such as New York and California are struggling to test widely for the coronavirus. The continued delays have made it impossible for officials to get a true picture of the scale of the growing outbreak, which has now spread to 36 states and Washington, D.C.

Nadine Dorries, the British health minister, confirmed reports late on Tuesday that she had tested positive for the coronavirus. She had attended a reception at Prime Minister Boris Johnson’s official residence two days earlier.

Ms. Dorries said in a post on Twitter that she had felt “pretty rubbish,” but hoped that the worst of the viral illness had come and gone. British news reports said she was the first member of Parliament to test positive.

Health officials were rushing to trace her contacts, which included dozens of constituents and lawmakers, as well as co-workers at the Department of Health and Social Care, according to British news outlets. She was at 10 Downing Street, Mr. Johnson’s residence, on Sunday for International Women’s Day.

The news prompted discussion in Britain about whether Parliament would need to be suspended. Lawmakers meet in the cramped House of Commons, sitting shoulder to shoulder on green leather benches and often spilling into the aisles and standing room areas, creating fertile conditions for illness to spread.

Some observers noted that Ms. Dorries appeared to have voted in the House of Commons about a week ago, meaning she had at least brief contact with other lawmakers at a time when she was presumably contagious.

But her most dangerous contact may have been with her 84-year-old mother, who is staying with her, Ms. Dorries wrote on Twitter late Tuesday night. “Thanks for so many good wishes,” Ms. Dorries wrote, adding that her mother had developed a cough. “She is being tested tomorrow,” she wrote. “Keep safe and keep washing those hands, everyone.”

Washington State prepares to restrict gatherings as a crisis in U.S. grows.

Gov. Jay Inslee of Washington State will announce on Wednesday a prohibition on community gatherings of 250 or more people in the Seattle area as the state takes extraordinary steps to contain a coronavirus outbreak, according to a person involved in the discussions.

The announcement, according to the person involved, is expected to target events such as sporting and entertainment gatherings while offering exceptions to things like retail stores.

Schools will not be affected, but districts will be expected to review things like sporting events that may draw significant crowds.

Washington State and the Seattle area have adopted increasingly stringent controls as the number of confirmed coronavirus cases has approached 300 — the most in the country — and the number of deaths has reached 24.

There will be no live audience. No spin room. Virtually no traveling members of the press. This is a presidential primary debate in the age of coronavirus.

CNN and Democratic officials announced on Tuesday that “at the request of the campaigns and out of an abundance of caution,” the Democratic debate in Phoenix on Sunday between Joseph R. Biden Jr. and Senator Bernie Sanders would be a significantly pared-down affair.

The live audience — whose jeers and cheers can be a major variable for the candidates onstage — will be missing. Instead, Mr. Biden and Mr. Sanders will debate each other in an empty theater, joined only by a handful of moderators and television crew members.

The spin room, where campaign aides scramble after the debate to declare their candidates a winner in front of packs of deadline-addled reporters, is scrapped as well, along with the media filing center, the often-cavernous space where hundreds of political reporters gather to watch the television broadcast and write their reports.

The Democratic National Committee, which oversees the debates, said Arizona officials had told them the event “could proceed as planned.” But the party said it wanted to take additional measures to ensure “the safety of our staff, campaigns, Arizonans and all those involved in the debate,” a party spokeswoman, Xochitl Hinojosa, said in a statement.

The debate, scheduled for 8 p.m. to 10 p.m. Eastern time on Sunday, was expected to follow a town hall-style format, where the candidates would respond to some questions posed by voters. CNN said that, at the moment, there were no plans to modify the format.

A prime-time debate with no in-house audience would be a highly unusual moment in the age of mass media campaigns, although it hearkens back to earlier days when presidential debates occurred in the privacy of closed television studios.

Mr. Sanders and Mr. Biden both called off primary night campaign events Tuesday as they awaited the results of voting in six states.

Common questions from parents about the coronavirus, and other ways to prepare.

Here are some of the most common questions that readers are asking today about how they can prepare for the coronavirus, how they can boost their immune systems and how they should react to the market (don’t, probably).

Reporting was contributed by Sheri Fink, Mike Baker and Benjamin Mueller.