The Wuhan coronavirus has killed nearly 500 people and infected more than 24,000. Here’s everything we know about the outbreak.

A girl wears a face mask at Beijing's central railway station.

A girl wears a face mask at Beijing’s central railway station.
Kevin Frayer/Getty Images

The death toll of a coronavirus outbreak sweeping China has reached at least 494, with more than 24,000 people infected as of Tuesday morning.

A man in the Philippines became the first person to die of the virus outside of mainland China on Saturday, followed by a 39-year-old man in Hong Kong on Tuesday.

The virus has spread to every province and region in China as well at least 25 other countries. Both the death toll and number of infected patients in mainland China has exceeded that of the 2003 SARS outbreak there (though SARS killed more people in total).

The virus might have jumped from animals to people at a market in the city of Wuhan. Outside of 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 11 cases so far: Six people in California; a husband and wife in Chicago, Illinois; a man in his 30s in Washington state; one patient in Arizona; and one in Massachusetts.

The World Health Organization declared a public-health emergency last week 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.

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The virus’ pneumonia-like symptoms include fever and difficulty breathing.

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According to the Centers for Disease Control and Prevention (CDC), 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 1 to 14 days, during which time carriers can be infectious.

The virus has killed at least 494 people in China and abroad.

A man leaves a medical center in Wuhan, China.
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, but one victim was a 36-year-old man.

More than 24,000 people have been infected.

The virus has spread to at least 25 other countries.

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Few children have been infected, but Chinese authorities reported that a baby was diagnosed just 30 hours after being born.

A child wears a face mask at the Ninoy Aquino International Airport in Manila, Philippines, on February 3, 2020.
Ezra Acayan/Getty Images

Other one-off cases of the virus in children include a nine-month-old girl in Beijing, a child in Germany whose father was diagnosed with the virus as well, and a child in Shenzhen who was infected but displayed no symptoms.

Still, the virus seems to mostly affect 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.

Last week, the World Health Organization (WHO) declared the coronavirus outbreak a global public-health emergency.

The World Health Organization assembly in Geneva in May 2008.

"Over the past few weeks, we have witnessed the emergence of a previously unknown pathogen, which has escalated into an unprecedented outbreak," WHO 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 last 14 days.

Donald Trump speaks about lowering drug prices with Health and Human Services Secretary Alex Azar on May 11, 2018.

The ban went into effect on February 2, with exceptions made for immediate family of American citizens and permanent residents.

US citizens returning home who have been in China's Hubei province within the prior 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 last week.

The total number of cases internationally has far surpassed that of the SARS outbreak.

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SARS also originated in China. It killed 774 people from November 2002 to July 2003.

A doctor checks equipment at a SARS screening room at Kuala Lumpur International Airport in Malaysia in 2003.
AHMAD YUSNI / AFP) (Photo by AHMAD YUSNI/AFP via Getty Images

Chinese authorities launched an investigation into the new coronavirus in early January. So far, health experts think it is not as deadly as SARS. The two belong to the same coronavirus family.

This chart shows the rate at which the new coronavirus has spread.

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But the true number of infected people is probably higher than the official total.

Medical workers walk near the Jinyintan hospital in Wuhan, which houses patients with the coronavirus, on January 10, 2020.

On January 26, academics from Imperial College London estimated that the true number of infected people could be about 100,000.

Health officials think the coronavirus might have jumped from animals to people at a seafood market in Wuhan.

The Huanan Seafood Wholesale Market in Wuhan, China, which was sealed off after being identified as the epicenter of a new virus.
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 from among people.

One study suggested that the virus may have initially jumped from bats to snakes to humans, but that's unlikely. Pigs or civets are the most likely intermediaries.

A snake-soup shop in Hong Kong.
Reuters/Bobby Yip

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 is clearly a "mammalian virus."

The US has confirmed two cases of human-to-human transmission.

REUTERS/Athit Perawongmetha/File Photo

In Chicago, Illinois, 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 last week, and the woman is reportedly doing well, too.

In San Benito County, California, a 57-year-old man passed the virus to his wife after returning from Wuhan. Both were transferred via ambulance to a hospital in San Francisco after their conditions worsened on Sunday.

The risk in the US is still low, according to the CDC.

There are no vaccines to prevent humans from contracting a coronavirus.

Medical staff members carrying a patient into the Jinyintan hospital, where patients infected by a coronavirus were being treated, in Wuhan on January 18.
STR/AFP via Getty Images

Travelers should wash their hands frequently with soap and water, making sure to scrub for at least 20 seconds, the CDC says.

Travelers should avoid touching their eyes, nose, or mouth with unwashed hands.

Travelers arriving on a flight from China at Seattle-Tacoma International Airport.

Wearing a mask is unlikely to be your best defense.

"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."

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.

On January 23, local officials quarantined the city of Wuhan by shutting down all transportation.

All of the city's public transportation - including buses, metros, and ferries - was halted. 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 at least 16 cities in 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 so far affect around 45 million people.

Doctors in Wuhan have reported that there aren't enough resources to treat a rising tide of patients.

Medical staff members at the Zhongnan hospital in Wuhan.
STR/AFP via Getty Images

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.

Guards at Hankou Railway Station on January 22 in Wuhan.
Xiaolu Chu/Getty Images)

Mimi Lau, a reporter at the South China Morning Post, said on January 23 that patients in Wuhan hospitals had likened getting a kit to winning the lottery.

The city built a hospital in just 10 days. A second one is almost finished.

Construction on the first hospital, the Wuhan Huoshenshan Hospital, started on January 23. The facility - which is around 269,000 square feet and includes 1,000 beds - welcomed its first patients on Monday.

The second hospital, the Leishenshan Hospital, will be slightly larger: 323,000 square feet with 1,300 beds. The site's construction started January 27, and the building is due to open on Thursday.

Airports around the world have implemented screening protocols.

Public health officials run thermal scans on passengers arriving from Wuhan at Suvarnabumi Airport on January 8 in Bangkok.
Lauren DeCicca/Getty Images

Twenty US airports - including New York's JFK airport, Los Angeles International Airport, and Chicago's O'Hare airport - 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.

A picture uploaded to social media on January 25 by the Central Hospital of Wuhan showing medical staff in Wuhan.

The US government evacuated some 200 Americans from Wuhan last week. The passengers arrived at the March Air Reserve Base in Riverside, California on January 29. They've been placed under a 14-day quarantine.

On Wednesday, another set of roughly 350 evacuees arrived in the US. They will be quarantined at two California military bases: the Travis Air Force Base in Fairfield and the Miramar Marine Corps Air Station in San Diego.

Japan also evacuated around 206 Japanese citizens from Wuhan. Twelve of those passengers were hospitalized in Japan after they reported feeling unwell or showed flu-like symptoms.

Malaysia, Indonesia, South Korea, India, Australia, Italy, France, the UK, and Turkey have evacuated citizens from the Hubei province as well.

Japan quarantined a cruise ship with more than 3,700 people after at least 10 passengers tested positive for the virus.

Medical staff testing passengers onboard The Diamond Princess for the Wuhan coronavirus.

The ship - known as the Diamond Princess - arrived in Yokohama, Japan, on Monday after a trip to Hong Kong. It was quarantined on January 31 after an 80-year-old passenger tested positive for the coronavirus.

"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. "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.

Passengers arrive at LAX from Shanghai, China, January 26, 2020.

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.

Health officers screened arriving passengers from China with thermal scanners at Singapore Changi Airport on January 22 as authorities increased measures against the coronavirus.
ROSLAN RAHMAN/AFP via Getty Images

The outbreak came as hundreds of millions prepared to travel for the weeks-long Lunar New Year, which is one of the largest annual human migrations in the world.

Passengers waiting to board trains at Shanghai's Hongqiao Railway Station ahead of the Lunar New Year in February 2018.
Aly Song/Reuters

The holiday started January 25, and 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 last week.

Shanghai Disneyland is temporarily closed, along with other attractions.

Bobby Yip/Reuters

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."

      • Rosie Perper contributed to this report.
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