The American man who was infected with China's new coronavirus came in close contact with at least 16 people before he was put in isolation, health officials revealed as they warned that there will likely be more cases in the US.
The unnamed man from Washington state, who is in his 30s, was publicly confirmed as the first Westerner infected with the virus on Tuesday, January 21.
Officials in the US now say the may have encountered – and therefore potentially infected – 16 or more people in America since catching the bug.
He wasn't diagnosed until Monday, January 20, after returning home from China five days earlier and becoming ill later that week.
The coronavirus, a SARS-like disease, has killed 17 and sickened at least 632 people worldwide - including in Thailand, Japan, Taiwan, South Korea and the US - since the first cases were reported in Wuhan, China, in late December.
Scientists estimate the true number of people infected since the outbreak began is in the thousands, possibly higher than 9,000.
The virus, called 2019-nCoV, is thought to have spread into humans from a Wuhan seafood market where wild animals were allegedly traded illegally.
International concern has grown with the revelation that the virus spreads not just from animals to people, but between people, likely in a similar way to how colds spread - but experts don't yet know how quickly this can happen.
On Thursday, Washington state Health Secretary John Wiesman said public health officials are well-equipped to handle and contain outbreaks - and predicted that the number of Americans infected would grow.
'I would expect that at some point we're going to have more cases in the US,' Wiesman said.
The US patient who became the first recorded case of the new coronavirus in America is a resident of Snahomish County in Washington State and is currently at Providence Regional Medical Center in Everett (pictured)
The Washington patient is said to be in good condition and recovering at Providence Regional Medical Center in Everett.
He is reportedly being observed in a guarded bio-containment room with a robotic stethoscope to limit physical contact with hospital staff.
The chief medical officer at Providence Regional Medical Center, Dr Jay Cook, said he had visited the man yesterday and that he was 'resting comfortably'.
'I had the opportunity to go by the unit early this morning, the patient was asleep, so I didn't wake him up, but the staff reported that he had a really good night,' Cook told CBS News.
The patient, who lives alone in Snahomish County, north of Seattle, had traveled by himself from Wuhan but did not visit any of the markets at the epicenter of the outbreak, according to state health officials.
He did not fly directly home from Wuhan, but arrived on January 15, the day before screening was in place and before he developed symptoms.
He reportedly recognized his own symptoms after seeing online coverage of the virus and sought treatment the same day, January 16.
The patient was tested on the 17th and his diagnosis was confirmed on Monday the 20th, health officials said.
Officials emphasized that risk to the public is low and said there was no reason to panic.
Janet Baseman, a professor of epidemiology in the School of Public Health at the University of Washington, told the Daily Beast that the Washington patient was 'very, very, very unlikely' to have transmitted the disease to anyone else because went in for treatment immediately after showing symptoms.
'Usually people do not transmit viruses like this to other people until they have symptoms themselves,' Baseman said.
Health authorities said they began reaching out to everyone who came into contact with him on Tuesday to check whether they are showing symptoms, which can include fever, cough and runny nose.
'All the close contacts will be part of what we call "active monitoring",' Wiesman said.
'That means that a public health worker will call the person daily to do a symptom check for them, see if they have a fever, cough, any respiratory issues.
'And should anyone develop symptoms at any point in time, these people who are under monitoring will be instructed to immediately call a public health worker to report the symptoms, and then we would help facilitate a medical evaluation.'
Wiesman defined close contact as a person who was within six feet of the patient for a prolonged period of time.
Officials have no recommended isolation for those people unless they develop symptoms, at which point they would be infectious.
Chinese authorities say 17 people have died and more than 500 have been infected, air and rail departures from Wuhan are suspended from January 23
So far, people suspected or confirmed to have the coronavirus have been put into isolation as quickly as possible because experts are unsure of how contagious it is.
Potential patients in China have been pictured being moved around inside plastic whole-body tubes to avoid exposing health workers.
At least 15 medics have already become infected in Wuhan.
All 17 patients who've died from the virus were in and around Wuhan. They ranged in age from 48 to 89, with an average age of 73.
Wuhan, a city of 11 million people, is now on lockdown as public transport has been halted and citizens told not to leave the city except in an emergency.
The Chinese city of Wuhan, where the outbreak is believed to have originated and all 17 deaths have happened, is now on lockdown and residents have been told not to leave the city unless in an emergency (Pictured: People shopping in Wuhan today, January 23)
Airports in the US are setting up screening for patients arriving from Wuhan in China. Pictured: People wearing masks as they arrived at Los Angeles International Airport on Wednesday
Following confirmation of the first American case, the US Centers for Disease Control and Prevention (CDC) announced a plan to 'funnel' all inbound passengers from Wuhan to five major US airports equipped to screen for the virus.
Screening checkpoints were set up at Los Angeles International Airport, New York's John F Kennedy airport and San Francisco International Airport last week and additional checkpoints are being installed at O'Hare International Airport in Chicago and Hartsfield-Jackson airport in Atlanta by the end of this week.
President Donald Trump said earlier this week that the US 'has it totally under control', adding 'we do have a plan, and we think it's going to be handled very well'.
Dr Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, called the first US case 'concerning' on Tuesday and said she expected additional cases.
WHAT IS THE NEW CORONAVIRUS SPREADING OUT OF CHINA?
An outbreak of pneumonia-like illnesses began in Wuhan, China, at the end of 2019.
Its symptoms are typically a fever, cough and trouble breathing, but some patients have developed pneumonia, a potentially life-threatening infection that causes inflammation of the small air sacs in the lungs.
Scientists in China recognized its similarity to two viruses that turned into global killers: SARS and MERS.
SARS, or severe acute respiratory syndrome is caused by the SARS coronavirus, known as SARS Co, and first emerged in China in 2002.
By the end of the outbreak, the virus had spread to several other Asian countries as well as the UK and Canada, killing 774.
MERS, or Middle East respirator syndrome originated in the region for which it's named, ultimately killed 787 people and belongs to the same family of coronaviruses as SARS.
The new virus wasn't a match for either of those two, but it did belong to the same coronavirus family.
Coronaviruses are a large family of pathogens, and most cause mild respiratory infections - i.e. the common cold.
But because the SARS and MERS proved deadly, the emergence of another new coronavirus has health officials on edge around the world.
Like its two dangerous cousins, the new coronavirus appears to have originated with animals - particularly seafood, chickens, bats, marmots - found at a Wuhan market that's been identified as the epicenter of the outbreak.
The symptoms of SARS, which may be similar to those of the new coronavirus, include:
After these symptoms, the infection will begin to affect your lungs and airways (respiratory system), leading to additional symptoms, such as:
So far, there isn't a treatment for the new virus or SARS, though the new virus has been sequenced, allowing for rapid diagnostics.