Today's biggest developments:
Here's how the day unfolded. All times are Eastern.
7:30 p.m. California declares state of emergency
Gov. Gavin Newsom declared a state of emergency after announcing California had 53 confirmed cases of novel coronavirus, including one death.
The deceased patient was a resident of Placer County and aboard a Princess cruise ship that traveled from San Francisco to Mexico last month. The boat is currently at sea and is slated to return to San Francisco soon.
Newsom said he delayed the cruise ship’s arrival to give federal officials more time to prepare. The CDC will be flying testing kits to the cruise ship before being turned around in a matter of hours on shore.
6 p.m. Pence calls COVID-19 tests 'essential health benefit'
Medicare and Medicaid, in addition to private insurers, will cover tests for the coronavirus because such examinations are an essential health benefit, Vice President Mike Pence said.
Pence didn't elaborate on what would happen for uninsured Americans.
5:30 p.m. 2nd California cruise passenger diagnosed
Diamond Cruises revealed a second passenger aboard the Feb. 11 to 21 voyage of the Grand Princess has contracted the coronavirus.
The Sonoma County, California, resident showed atypical "gastrointestinal and cardiovascular symptoms," the company said.
A Grand Princess passenger who lived in Placer County died from the disease, according to health officials.
5 p.m. LAX health screener tests positive
A medical screener at LAX Airport in Los Angeles has tested positive for the virus, according to the Department of Homeland Security.
The screener, whose last shift at the airport was on Feb. 21, began experiencing flu-like symptoms about eight days later, according to DHS. The individual at that point visited a doctor and tested positive.
"We are told the individual wore all the correct protective equipment and took necessary protections on the job," DHS spokeswoman Heather Swift said in a statement.
DHS said it's working to identify which coworkers the individual came in contact with and whether the virus was contracted from a traveler.
4:30 p.m. Seattle confirms 10 new cases
Seattle health officials said the city's latest coronavirus death is among the 10 cases confirmed on Wednesday.
The patient who died was described as a woman in her 90s who lived at Life Care, the nursing home at which multiple cases and deaths have been reported.
4:15 p.m. Italy bans fans from sports stadiums
Italy's government has declared that sporting events will continue but fans won't be allowed to attend, because of fears over the coronavirus.
The decision will cover all matches, mostly soccer and rugby, over the next month. Six matches in the nation's top-flight soccer league, Serie A, were postponed last week.
4 p.m. Dow adds almost 1,200 points
After a volatile few weeks amid coronavirus uncertainty, U.S. financial markets rallied sharply on Wednesday.
The Dow Jones Industrial Average soared 1,173.45 points, or 4.53%, while the S&P 500 and Nasdaq each 4.22% and 3.85%, respectively. The surge came after massive losses Tuesday despite the Federal Reserve announcing a rare emergency rate cut.
Lawmakers on Wednesday announced an $8 billion deal to help combat the outbreak, a move that also appears to have put more investors at ease.
Among the biggest winners on Wednesday were health insurance companies, possibly due to Joe Biden's big wins on Super Tuesday over Bernie Sanders.
3:52 p.m. 2nd New York family infected
A second family in Westchester, New York, has contracted the coronavirus, according to Gov. Andrew Cuomo.
The father of the family came in contact with the Westchester attorney who had been diagnosed earlier, and contracted the virus along with his wife, two sons and one daughter, Cuomo said. One of the family's daughter's tested negative, the governor said.
The number of confirmed cases in New York state is now 11, and Cuomo warned that the number of infected Westchester residents will increase.
"It is going to be dozens and dozens and dozens," he said.
3 p.m. United reduces flights in April
United Airlines announced it will reduce domestic flight schedules by 10% and international flights by 20% in April due to declining demand.
The airline said it would reveal more specifics about the reductions on Saturday and is mulling a similar reduction in May.
United also is offering employees the option to voluntarily apply for an unpaid leave of absence, instituting a hiring freeze and suspending 2019 merit salary increases until July.
2:25 p.m. 11th person reported dead, 1st in California
Officials in Placer County, California, announced an elderly adult with underlying conditions was the 11th coronavirus death.
The patient was exposed during international travel between Feb. 11 and 21 aboard a Princess Cruise ship that departed from San Francisco to Mexico, according to health officials, who are working to identify and contact other passengers who may have been exposed.
Princess Cruises issued a statement to guests and crew who are currently aboard the ship, the Grand Princess, telling them about the situation and advising guests who sailed on the previous voyage to stay in their stateroom until they are cleared by medical staff. The company said it canceled the boat's docking at Ensenada, Mexico, and will return to San Francisco on Thursday afternoon.
The deceased patient had minimal community exposure between returning from the cruise to their arrival at Kaiser Permanente Roseville Medical Center on Feb. 27, the officials said. However, 10 hospital health care workers and five emergency responders who were exposed to the patient before they were put into isolation are currently under monitored quarantined.
1:40 p.m. 10th coronavirus-related death recorded in US
Vice President Mike Pence, who is leading the White House's coronavirus task force, announced that a 10th American has died from the disease. Washington health officials later said the death occurred in King County, where eight other deaths were previously recorded.
Pence did not provide further detail about the patient, but said as of Wednesday afternoon a little more than 100 Americans have contracted the virus. Pence said he and the task force are slated to visit Washington state, where nine of the coronavirus deaths occurred, on Thursday.
1:15 p.m. 1,000 people in self quarantine in New York
New York Gov. Andrew Cuomo gave an update on the coronavirus situation in Westchester County, and said about 1,000 residents have been asked to self-quarantine.
At least eight employees at Lawrence Hospital, where a 50-year-old man who contracted the disease was first admitted, are being tested for the virus, according to Cuomo.
12:56 p.m. $8.3 billion for coronavirus emergency funds
Lawmakers in Washington reached a deal to allocate $8.3 billion towards the response to coronavirus.
The amount is nearly seven times as large as President Donald Trump's request and will fund the government's response, including vaccine development, support for state and local governments and assistance for affected small businesses.
12:39 p.m. Italy to temporarily close schools and universities
Schools and universities in Italy will close beginning Thursday until March 15, authorities announced.
The decision comes as the country grapples with rising confirmed cases of coronavirus and their attempts to contain it. There were 347 new confirmed cases reported in Italy overnight, making the total 2,036, according to the WHO's numbers as of Wednesday.
12:10 p.m. 6 new cases have been confirmed in LA County, state of emergency declared
Officials in Los Angeles County declared a state of emergency as six new positive cases of coronavirus were confirmed there in the last 24 hours.
Kathryn Barger, a supervisor on the county's board, said in a press conference the declaration "is not a response routed in panic." Instead, it will allow local officials to better coordinate with state and federal partners to "enhance our preparedness," she said.
Los Angeles County becomes the second county in the U.S. to declare a state of emergency. King County in Washington, which has reported eight deaths, declared a state of emergency on Monday.
Barbara Ferrer, the county's public health director, said the new cases are all linked to either travel history or a close contact with a confirmed case. There are not yet any known cases of community transmission, according to Ferrer.
11:51 a.m. Hospitals should be more proactive in testing, says member of president's coronavirus task force
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and a member of the president's coronavirus task force, said he feels "very strongly" that hospitals should be testing patients more proactively for coronavirus.
While testifying in a House Appropriations subcommittee hearing on the NIH budget, Fauci said the reason hospitals haven't done so yet is because there aren't enough resources to test the virus in every emergency room and health center. However, he noted, the CDC is expanding testing beyond the six sentinel cities it started with.
Fauci also made a point to note that the WHO fatality rate -- 3.4% -- is incomplete because the denominator of asymptomatic cases is currently unknown.
"If you look at the cases that have come to the attention of the medical authorities in China and you just do the math, the math is about 2%. If you look at certain age groups, certain risk groups, the fatality is much higher, but as a group it's going to depend completely on what the factor of asymptomatic cases are," he said.
11:32 a.m. Italy has begun screening US-bound passengers at airports
At airports in Rome and Milan, passengers will have their temperatures taken before departing for the United States amid the coronavirus outbreak, sources told ABC News on Wednesday. The screenings began Tuesday at Rome-Fiumicino and Milan-Malpensa airport, the sources said.
If someone does have a fever, they will be taken aside and not allowed to travel before further tests are carried out. The tests are being administered by the Ministry of Health and the Italian Red Cross. They are similar to ones that have now begun in South Korea.
11:02 a.m. South Korea to start screening US-bound travelers
As part of efforts to contain the coronavirus outbreak, all travelers flying from South Korea to the United States will now have their temperatures checked at their assigned gate at the airport prior to boarding their flight, the South Korean Ministry of Land, Infrastructure and Transport announced Wednesday.
Travelers who have a body temperature higher than 37.5 degrees Celsius (99.5 Fahrenheit) will not be allowed to board their flight. Tickets will be refundable, the ministry said.
10:37 a.m. Case count in New York rises to 6
The number of confirmed coronavirus cases in New York state climbed to six on Wednesday.
The four new cases confirmed Wednesday are tied to a 50-year-old patient from New Rochelle in New York's Westchester County. The man's wife, their two children and a neighbor who drove him to the hospital have all tested positive for the novel coronavirus, New York Gov. Andrew Cuomo said at a press conference.
The man's son is a 20-year-old student at Yeshiva University in New York City. His daughter is a 14-year-old student at Salanter Akiba Riverdale Academy and High School, known as SAR, in the Riverdale neighborhood of the Bronx. Both schools announced closures Wednesday upon receiving word of their infections, according to Cuomo.
New York City Mayor Bill de Blasio said the son had not been on Yeshiva University's campus since Feb. 27. Both the son and daughter, as well as their mother, remain at home in isolation.
"Yeshiva University is working closely with the Department of Health and Mental Hygiene to take every necessary precaution to ensure the safety of students and the community," de Blasio said in a statement Wednesday. "City disease detectives are on campus to identify close contacts of the student and connect those individuals to testing immediately. As of this morning, two contacts have transferred to Bellevue Hospital for testing. We will continue working closely with our state partners to ensure we are doing everything we can to keep New Yorkers safe."
Meanwhile, students from both the State University of New York (SUNY) and the City University of New York (CUNY) will be recalled from study abroad programs in China, Iran, Italy, Japan and South Korea, according to Cuomo. They will be flown back to the United States on a chartered plane, which will land at Stewart International Airport in New Windsor, New York. The students will then be quarantined for 14 days in dormitories.
9:50 a.m. Son of New York patient tests positive
A college student in New York has tested positive for the novel coronavirus after his father became infected, officials said.
Yeshiva University in New York City confirmed in a press release Wednesday that the student had tested positive for the newly discovered virus, known officially as COVID-19.
"Our thoughts and prayers are with him and his family as well as to all those affected," the school said in a statement.
As a precautionary measure, the school canceled all Wednesday classes on its Wilf Campus in the Washington Heights neighborhood. All classes and operations at the school's other campuses will continue as normal.
"This precautionary step will allow us to work with city agencies and other professionals to best prepare our campus," the school said, "and ensure the uncompromised safety of our students, faculty and staff."
8:19 a.m. New Hampshire's 1st patient told to stay isolated but went to event instead, officials say
The first confirmed case of the novel coronavirus in New Hampshire is a hospital employee who went to an event despite being told to stay isolated, officials said.
Through the course of an investigation, officials at the New Hampshire Department of Health and Human Services learned that the patient had attended an invitation-only private event last Friday after being told to self-isolate. The department has issued an official order of isolation to the patient and is contacting attendees who had close contact with the individual during the event to notify them to follow the recommended 14-day self-isolation, according to a press release on Tuesday.
Now, there's a second presumptive positive case involving a person who was in close contact with the state's first patient. The second individual is a man from Grafton County who is currently isolated at home, and state officials have begun tracing his contacts. The New Hampshire Department of Health and Human Services is awaiting confirmation of two presumptive positive test results by the U.S. Centers for Disease Control and Prevention.
"We expect additional cases may be identified that are related to this investigation," officials said in the press release.
Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire, confirmed that the state's first patient is an employee.
7:48 a.m. 1st confirmed case at EU office
The first case of the novel coronavirus has been confirmed at a European Union office in Brussels, a spokesperson told ABC News.
The case is a male employee who works at the European Defense Agency and had recently traveled to Italy, where 2,236 people have been infected with the newly identified virus. The man tested positive Tuesday, according to EU press officer Claire Joawn.
6:50 a.m. Outbreak in South Korea shows little signs of slowing down
The South Korean city of Daegu reported another spike in new cases of the novel coronavirus overnight as the outbreak shows little signs of slowing down there.
South Korea's Centers for Disease Control and Prevention recorded an additional 516 confirmed cases in the past 24 hours, bringing the country's total to 5,328. Over 400 of the newly confirmed cases were in Daegu, where a secretive religious sect has been linked to a majority of the country's infections.
South Korea has the second-highest national total of confirmed cases, behind China.
5:45 a.m. COVID-19 is deadlier than the flu, WHO says
The disease caused by the novel coronavirus, known officially as COVID-19, is more than three times as deadly as the season flu, according to the head of the World Health Organization.
"Globally, about 3.4% of reported COVID-19 cases have died," WHO Director-General Dr. Tedros Adhanom Ghebreyesus said at a press conference in Geneva on Tuesday. "By comparison, seasonal flu generally kills far fewer than 1% of those infected."
Although the newly identified virus does not spread as easily as the flu, it causes more severe illness and there are currently no vaccines or therapeutics.
"While many people globally have built up immunity to seasonal flu strains, COVID-19 is a new virus to which no one has immunity," Tedros said. "That means more people are susceptible to infection, and some will suffer severe disease."
3:30 a.m. New presumptive positive case reported in Northern California
Public health officials in Northern California's Placer County have reported a second case of the novel coronavirus after a hospitalized patient tested "presumptively positive," pending confirmation from the U.S. Centers for Disease Control and Prevention.
In a press release issued late Tuesday night, Placer County Public Health said the patient is an older adult whose exposure to the newly identified virus, known officially as COVID-19, likely occurred during their time on a Princess Cruises ship that traveled from San Francisco to Mexico last month. It's the same cruise associated with a confirmed case announced previously in Sonoma County.
"As the case appears connected to travel, it most likely does not represent an instance of local community spread," Placer County Public Health said in the press release.
The Placer County patient is critically ill and in isolation at a local hospital. Close contacts of the individual are being quarantined and monitored.
The county has declared a local health emergency as well as a local emergency.
“We expect to see additional cases in coming days, including cases of community spread, not linked to travel," said Health Officer Dr. Aimee Sisson. “We are declaring these emergencies today so we will be able to activate and deploy resources to adequately respond to an increase in cases."
As of Tuesday, the CDC counted 108 confirmed and presumptive positive cases of COVID-19 in the United States. That number includes 60 Americans whose cases were confirmed by the local U.S. health systems, 45 who were repatriated from the Diamond Princess cruise ship quarantined off the coast of Japan and three who were repatriated from Wuhan, China, where the virus emerged back in December.
So far, nine people sickened with the virus in the United States have died.
More than 80,000 people have been infected with the virus in China, mostly in central Hubei province, which includes Wuhan, the epicenter of the outbreak, and nearly 3,000 of them have died. Meanwhile, over 10,000 have tested positive for the virus in 72 other nations and 166 have died, according to the latest data from the World Health Organization, which has declared the outbreak a global health emergency.
ABC News' Catherine Thorbecke, Trish Turner, John Parkinson, Ben Gittleson, Joohee Cho, Dragana Jovanovic, Aaron Katersky and Phoebe Natanson contributed to this report.