As the global death toll passed 3,000, South Korea said Monday it has confirmed 599 new cases, far higher than the daily tally reported in China. With 4,335 confirmed infections and at least 22 deaths, South Korea has the second-largest national caseload. However, it has tested more than 100,000 people, far more than most nations.

In the United States, the death toll has reached six after four more people in Washington state were reported deceased. At a news conference Monday, King County Executive Dow Constantine issued an Emergency Declaration for what has become the epicenter of a coronavirus outbreak in Washington state. There are now 14 cases in King County and another four in Snohomish County. A genetic analysis has suggested that the novel coronavirus, which causes a highly infectious respiratory disease called covid-19, has probably been spreading undetected for about six weeks in Washington state. The U.S. Food and Drug Administration on Saturday took steps to sharply expand testing.

Around the country, school districts have undertaken massive preparations to lessen the risk of exposure and get ahead of any possible outbreaks, according to The Associated Press. The measures range from online lesson planning to deep-cleaning schools to kill viruses.

Elsewhere in the Pacific Northwest, presumptive cases of the virus have led to individual closures, including at least two other high schools and two elementary schools in the Seattle area, and at an elementary school just outside Portland, Oregon.

And in Rhode Island, three Catholic schools have temporarily shut down in response to three likely positive cases among students or staff who went on an educational trip to Europe.

Vice President Mike Pence on Monday briefed governors on the federal response and preparations for the coronavirus, according to Maryland Gov. Larry Hogan, a Republican. Pence, head of the White House Coronavirus Task Force, told the governors that he would convene a weekly teleconference on the virus. Pence was scheduled to brief senators from both major parties later Tuesday.

Texas Gov. Greg Abbott is calling on the Centers for Disease Control and Prevention to cancel the release of dozens of people scheduled to leave quarantine Monday in the San Antonio area and demanding that it perform another round of tests after officials mistakenly released a woman who had tested positive for the novel coronavirus.

Abbott, a Republican, said after a news conference that he expects those in quarantine would not be going home.

The governor’s words echo those of San Antonio and Bexar county elected leaders who were incensed to learn that the patient had been mistakenly released Saturday and spent 12 hours in the community before the CDC took her back into isolation.

San Antonio Mayor Ron Nirenberg said the woman visited the North Star Mall, ate at the food court and stayed at the Holiday Inn Express near the city’s airport. The woman arrived in Texas in February from China’s Wuhan province and was part of a cohort of 91 individuals brought to the region.

The woman had been asymptomatic and initially tested negative for the virus in two tests, meeting the CDC’s criteria for release. After she was let go, the CDC obtained the results of a third test showing a “weakly positive” confirmation of the virus that causes covid-19.

Meanwhile, about 140 evacuees from the Diamond Princess cruise ship headed home Monday after being released from a 14-day quarantine at Travis Air Force Base in Fairfield, California.

Those released showed no signs of coronavirus, a CDC spokesman confirmed to The Washington Post on Monday.

Busloads of evacuees left the base around 7 a.m. and were headed to San Francisco International Airport and Sacramento International Airport for their flights home.

“They were very much smiling when they left,” CDC spokesman Scott Pauley said of the early morning departures.

Monday’s departures mark the last major wave of evacuees from the cruise ship to be released. There were 180 evacuees released Feb. 18, and 53 followed two days later, Christian Conrad, a spokesman for Travis Air Force Base, told The Washington Post. Fewer than 10 people remain in quarantine at the base, though their conditions were unclear.

Italy now has more than 1,600 confirmed cases, while Iran surpassed 1,500, with 66 deaths. Travelers from both countries appear to have spread the virus to other nations in the Middle East and Europe. Elsewhere, Indonesia, one of the few large nations thought to be free of the virus, said Monday that it had two confirmed cases, while others were reported from Australia to India to Portugal.

Officials are expecting more cases in other countries. “It is no longer possible to absolutely prevent new cases coming in,” Brendan Murphy, Australia’s chief medical officer, told reporters Monday. British Prime Minister Boris Johnson said the day before that he expected the outbreak to “spread a bit more” in Britain, where there are 39 confirmed cases.

British Airways on Monday said it was canceling hundreds of flights — including a dozen between London and New York — in response to the coronavirus outbreak.

In an emailed statement, British Airways said that it was canceling flights between March 16 and March 28 “to match reduced demand due to the continuing coronavirus issue.”

The announcement came on the same day that Dublin-based Ryanair, a popular low-cost airline, said that it was reducing its flights, mainly to and from Italy, by up to 25 percent for three weeks starting on March 17.

In an emailed statement, the airline added that there had been a “significant step up in passenger no-shows on flights, particularly from and within Italy.”

In addition to reducing flights, airline executives said that they were meeting daily to discuss the issue and had put in place a number of measures to address the “current downturn in business caused by the Covid-19 Virus.” These include a “rolling schedule cuts as booking patterns alter,” unpaid vacation time for pilots and pay freezes.

Hundreds of Israelis are in quarantine over concerns that they might have come into contact with people infected with coronavirus. But that won’t keep some of them from voting.

Israel staffed special voting places just for individuals in quarantine to participate in Israel’s third national election in less than a year. Medical workers in full protective gear sat at the entrance to special tents set up for the occasion. Voters wore masks and gloves and could vote only if they were not showing symptoms and did not take public transportation to the polls.

Meanwhile, the morning after the United States reported its second coronavirus death, health and government officials continued to plead with Americans to stop buying precautionary face masks unless they are already sick or are health-care workers.

“It’s important for folks to know right now their risk as American citizens remains low,” U.S. Surgeon General Jerome Adams said on “Fox & Friends” on Monday morning. “There are things people can do to stay safe. There are things they shouldn’t be doing. One of the things they shouldn’t be doing, the general public, is going out and buying masks. It actually does not help, and it has not been proven to be effective in preventing the spread of coronavirus amongst the general public.”

Adams said that as a health-care worker, he has to get “fit tested” when wearing protective masks, and those who do not wear the masks properly tend to fidget with them or touch their faces, which “actually can increase the spread of coronavirus.”

The kind of mask that requires a “fit test” is called an N95 respirator. It should be worn tightly on a person’s face and is meant to protect the wearer by filtering out 95 percent of airborne particles, according to the CDC. The other kind, called a surgical mask, is loosefitting and is mostly intended to protect the patient or outside world from the wearer’s respiratory emissions. It is not considered to provide respiratory protection for the wearer.

The only people who should be wearing masks are healthy people who are taking care of someone who is sick or sick people who are coughing or sneezing when they are in public, according to the World Health Organization.