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A coronavirus outbreak that originated in Wuhan, China, has killed more than 1,000 people and infected more than 42,000.
The virus has spread to at least 25 other countries.
Two deaths have been reported outside of mainland China: one in Hong Kong and another in the Philippines.
Chinese authorities quarantined the city of Wuhan and many other cities, with all transportation halted.
The death toll of a coronavirus outbreak sweeping China has reached 1,013, with more than 42,000 people infected as of Monday evening.
A man in the Philippines and a 39-year-old man in Hong Kong mark the only two deaths outside of mainland China.
The virus has spread to every province and region in China as well at least 25 other countries. Both the death toll and the number of infected patients now exceed those of the 2003 SARS outbreak.
The zoonotic virus may have jumped from animals to people at a market in the city of Wuhan. Researchers suggest that the virus originated in bats, and one study suggests the disease might have spread from the endangered pangolin to people.
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Outside China, cases have been reported in Australia, Belgium, Cambodia, Canada, Finland, France, Germany, India, Italy, Japan, Malaysia, Nepal, the Philippines, Russia, Singapore, South Korea, Spain, Sri Lanka, Sweden, Taiwan, Thailand, the United Arab Emirates, the UK, the US, and Vietnam.
The US has reported 12 cases so far, the latest of which was confirmed in Wisconsin on February 6.
The World Health Organization has declared he outbreak a public-health emergency, and Chinese President Xi Jinping said the virus poses a "grave threat."
Here's everything we know:
The first case of the coronavirus was reported in Wuhan in December. The central Chinese city has a population of 11 million.
Ruobing Su/Business InsiderThe virus' pneumonia-like symptoms include fever and difficulty breathing.
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According to the Centers for Disease Control and Prevention, a person could be at risk if they have:
Fever and symptoms of lower respiratory illness, such as coughing or difficulty breathing, after traveling to Wuhan or having close contact with someone who was ill and is now under investigation for the virus in the past two weeks.
Fever or symptoms of lower respiratory illness after having close contact in the past two weeks with someone who's been confirmed to have the virus.
Chinese health officials say the incubation period for the virus ranges from one to 14 days, during which time carriers can be infectious.
The virus has killed at least 1,013 people.
Noel Celis/AFP via Getty Images
"The people who are likely to die first will have other illnesses," Adrian Hyzler, the chief medical officer at Healix International, which offers risk-management solutions for global travelers, told Business Insider. "But as it spreads, it'll pick up more people like flu does."
Most patients who died were elderly or otherwise unwell, according to Chinese officials.
More than 42,000 people have been infected.
The virus has infected at least 42,749 people as of Monday evening.
The virus has spread to at least 26 countries.
The total number of cases internationally has far surpassed that of the SARS outbreak.
This chart shows the rate at which the new coronavirus has spread.
But the true number of infected people is probably higher than the official total.
On January 26, academics from Imperial College London estimated that the true number of infected people could be about 100,000.
On February 7, a whistleblower doctor in Wuhan who was censored after sounding the alarm about the coronavirus died from the disease.
LI WENLIANG/GAN EN FUND via REUTERS
Li Wenliang, a 34-year-old doctor at the Central Wuhan Hospital, was one of the first people to sound the alarm about the new outbreak in December. He alerted a group of alumni from his medical school. But he was silenced by police in Wuhan and forced to sign a letter acknowledging he was "making false comments."
Li caught the coronavirus after treating patients. He died around 3 a.m. local time.
Few children have been infected, but Chinese authorities reported that a baby received a diagnosis just 30 hours after being born.
Ezra Acayan/Getty Images
Other one-off cases of the virus in children include a 9-month-old girl in Beijing, a child in Germany whose father had the virus as well, and a child in Shenzhen who was infected but displayed no symptoms.
Still, the virus seems to affect mostly adults. A study published in the New England Journal of Medicine earlier this month speculated that "children might be less likely to become infected or, if infected, may show milder symptoms" than adults.
Disease experts say it's good that the virus hasn't spread much among kids because children are less likely to wash their hands and cover their mouths — behaviors that can spread germs.
On January 30, the World Health Organization declared the coronavirus outbreak a global public-health emergency.
FABRICE COFFRINI/AFP via Getty Images
"Over the past few weeks, we have witnessed the emergence of a previously unknown pathogen, which has escalated into an unprecedented outbreak," the WHO's director-general, Tedros Adhanom Ghebreyesus, said. "We don't know what sort of damage this virus could do if it were spread in a country with a weaker health system. We must act now to help countries prepare for that possibility."
For now, the WHO doesn't recommend limiting the movement of travel and trade.
"This declaration is not a vote of no confidence in China," Ghebreyesus added. "I have never seen in my life this kind of mobilization."
The global-health emergency declaration has been used five times since it was created in 2005.
"They only do this for extraordinary illnesses that are of international concern," Hyzler said. "Suddenly the world is alerted to a much greater extent and they'll start pouring a lot more assistance and aid to airports, to transport hubs, and do their best to control this outbreak."
The Trump administration has imposed a travel ban on foreign nationals who have been in China within the past 14 days.
The ban went into effect February 2, with exceptions made for immediate family members of American citizens and permanent residents.
US citizens returning home who have been in China's Hubei province —where Wuhan is located — within the past 14 days may be quarantined for up to two weeks.
"The American public can be assured the full weight of the US government is working to safeguard the health and safety of the American people," Health and Human Services Secretary Alex Azar said in a briefing on January 31.
Health officials think the coronavirus may have jumped from animals to people at a seafood market in Wuhan where live animals were sold.
Photo by Noel Celis/AFP via Getty Images
They initially said the virus could spread only from animals to humans. But on January 20, Chinese officials confirmed that the virus could be transferred among people.
Researchers think the virus originated in bats. One study suggested that it might have initially jumped from bats to snakes to humans, but that's unlikely. Pangolins, pigs, or civets are the more likely candidates.
In a paper in the Journal of Medical Virology, researchers said the protein codes favored by the Wuhan virus closely resembled the protein codes in snakes. But Cui Jie, a virologist who helped identified SARS-related viruses in bats in 2017, said the strain from Wuhan was clearly a "mammalian virus."
On February 7, researchers at the South China Agricultural University suggested that the endangered pangolin may have been the intermediary species between bats and people.
SARS also originated in a Chinese market that sold live animals. It killed 774 people from November 2002 to July 2003.
AHMAD YUSNI / AFP) (Photo by AHMAD YUSNI/AFP via Getty Images
The new coronavirus appears to be more contagious but less deadly than SARS. The two belong to the same coronavirus family.
There are no vaccines to prevent humans from contracting a coronavirus.
STR/AFP via Getty Images
Five leading drug companies — Johnson & Johnson, Regeneron Pharmaceuticals, GlaxoSmithKline, Moderna, and Gilead Sciences — have announced plans to research and develop treatments for the new coronavirus.
In the US, 12 coronavirus cases have been confirmed across six states. A US citizen has also died from the virus Wuhan.
So far, six cases of the virus have been confirmed in California, along with a married couple in Chicago; a man in his 30s in Washington state; one patient in Arizona; one in Massachusetts; and a case in Wisconsin.
On February 6, the first US citizen died from the virus in Wuhan. The person was 60 years old. The New York Times reported it was a woman with underlying health conditions, citing two people familiar with the matter.
The risk in the US is still low, according to the CDC.
Two of the US patients transmitted the coronavirus to their spouses.
Kyodo News via Getty Images
In Chicago, a woman in her 60s transmitted the virus to her husband. She had recently traveled to Wuhan to care for her elderly father, but her husband did not travel with her. He is in stable condition, CDC authorities said, and the woman is reportedly doing well, too.
In California's San Benito County, a 57-year-old man passed the virus to his wife after returning from Wuhan. Both were transferred via ambulance to a University of California, San Francisco hospital after their conditions worsened.
To prevent the spread of the coronavirus, all travelers should wash their hands frequently with soap and water, making sure to scrub for at least 20 seconds, the CDC says.
Travelers should also avoid touching their eyes, nose, or mouth with unwashed hands. Wearing a mask is unlikely to be your best defense, however.
"There's little harm in it," Eric Toner, a scientist at Johns Hopkins Center for Health Security, told Business Insider. "But wearing masks, except in the situation of a healthcare provider, has never been shown to be a very effective way to protect yourself from infectious diseases."
Local officials have quarantined Wuhan by shutting down all transportation.
All of the city's public transportation — including buses, metros, and ferries — was halted on January 23. Trains and airplanes coming into and out of the city were also shut down, and roadblocks were installed to keep taxis and private cars from exiting.
Wuhan's 11 million residents were told not to leave the city, barring special circumstances.
China has imposed travel restrictions on the rest of the Hubei province.
Huanggang, a city of about 7.5 million people, placed its urban core under lockdown on January 23, closing subway and train stations as well as theaters and internet cafés.
Additional cities — Ezhou, Chibi, Xiantao, Zhijiang, Qianjjiang, Huangshi, Xianning, Yichang, Enshi, Xiangyang, Jingmen, Xiaogan, Dangyang, and Suizhou — have followed suit with their own travel restrictions.
The restrictions affect more than 50 million people.
Two new hospitals have been built in Wuhan. Construction on each lasted just 10 days.
Construction on the first hospital, the Wuhan Huoshenshan Hospital, started January 23. The facility — which includes 1,000 beds — welcomed its first patients on February 3.
The second hospital, the Leishenshan Hospital, is slightly larger with 1,600 beds. The site's construction started January 27, and the building was completed on February 6.
Doctors in Wuhan have reported that there aren't enough resources to treat the rising tide of patients.
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A doctor in Wuhan told the BBC on January 23 that thousands of patients were waiting for hours in line to receive medical care. Another doctor told the South China Morning Post that medical workers did not have enough protective gear — and that some were catching the virus as a result.
Test kits have reportedly been reserved for patients with the most severe symptoms. That means many diagnoses could be delayed.
Xiaolu Chu/Getty Images)
Chinese officials have warned that the virus is mutating, which could make it harder to control and treat.
Gao Fu, the director-general of China's Center for Disease Control and Prevention, said on January 22 that the virus was adapting and changing — making it harder to fight.
Airports around the world have implemented screening protocols.
Lauren DeCicca/Getty Images
Twenty US airports — including New York's John F. Kennedy, Los Angeles International Airport, and Chicago's O'Hare — have started screening passengers for the virus. Airports in Hong Kong, Singapore, Thailand, and South Korea are also screening people.
Several countries, including the US, have evacuated citizens and employees from China.
THE CENTRAL HOSPITAL OF WUHAN VIA WEIBO /via REUTERS
The US government has evacuated around 850 people from Wuhan since January 29.
The first set of 200 evacuees arrived at the March Air Reserve Base in Riverside, California, on January 29. They were placed under a 14-day quarantine.
On February 5, another set of roughly 350 evacuees arrived in the US. They are being quarantined at two California military bases: the Travis Air Force Base in Fairfield and the Miramar Marine Corps Air Station in San Diego. Of the 167 passengers who landed in San Diego, four were transported to local hospitals after showing symptoms of the virus, the CDC said.
Additional evacuees are being quarantined at the Lackland Air Force Base in San Antonio, Texas and the Eppley Airfield in Omaha, Nebraska.
Many other countries — including Japan, South Korea, Australia, France, and the UK — have evacuated citizens from China as well.
Japan quarantined a cruise ship with more than 3,700 people. At least 130 people on board have tested positive for the virus.
The ship — known as the Diamond Princess — arrived in Yokohama, Japan, on Monday after a trip to Hong Kong. It was quarantined January 31 after an 80-year-old passenger who had disembarked days earlier tested positive for the coronavirus. The passenger and 10 others who were diagnosed with the virus were taken into isolation at a nearby hospital on the Japanese mainland.
As of Monday, at least 130 cases of the virus had been confirmed on the ship.
"Cruise lines take public health issues very seriously — I've actually been quarantined myself on Diamond Princess in Japan," Liz Jarvis, editor of Cruise International Magazine, told Business Insider, referring to a time when she fell ill. "I know that passenger safety is absolutely paramount to all the team on board, and they act very swiftly in the event of any suspected issue."
The CDC issued a travel warning to avoid all nonessential travel to China.
The CDC raised its travel warning to a level three, the highest, which advises US citizens to avoid all nonessential travel to China.
On January 25, the Chinese government barred its citizens from booking overseas tours, flights, and hotel stays.
ROSLAN RAHMAN/AFP via Getty ImagesThe outbreak began as hundreds of millions of people prepared to travel for the weeks-long Lunar New Year, which is one of the largest annual human migrations in the world.
The holiday started January 25 and ended on February 8. Experts worried the surge in travel could boost the virus' spread.
"This couldn't have happened at a worse time for Wuhan," Hyzler said.
Beijing canceled its Spring Festival celebrations.
Shanghai Disneyland is temporarily closed, along with other attractions.
The park closed January 25 without saying when it would reopen. The announcement came at a time of peak spending at the park, which has said it will refund tickets.
The Badaling section of the Great Wall of China temporarily closed as well.
Chinese President Xi Jinping said last week that the country faced a "grave situation."
Sergei Chirikov/AP Images
Rosie Perper and Aylin Woodward contributed to this report.