Two months ago, reports surfaced out of China that a cluster of pneumonia cases in the central city of Wuhan may be due to a new type of coronavirus.
The World Health Organization said at the time it was still assessing the extent of the outbreak, but noted that there were no reports of novel coronavirus outside Wuhan.
Since then, the situation has drastically changed.
Many of the world's biggest sporting, entertainment and political events have all been suspended -- even some politicians have self-quarantined -- as more than 2,000 cases were confirmed in the U.S.
The WHO has now declared the virus, aka COVID-19, a pandemic.
Life has been upended. Here's how:
Elbow bumps have become the new normal as the Centers for Disease Control and Prevention warns the public not to shake hands.
Politicians, including Vice President Mike Pence and House Speaker Nancy Pelosi, have been seen tapping elbows to greet officials. Athletes have also used elbow bumps to greet opposing players on the field, though numerous sports organizations have since announced they're suspending their seasons.
And while elbow bumps aren't the only style of greeting to adopt -- bowing is another popular option -- health officials are steadfast on their recommendation: "Stop handshaking."
Politicians across the spectrum have been forced to respond as the novel coronavirus has pushed the 2020 presidential election into unchartered territory.
President Donald Trump has halted campaign events temporarily, with plans to shift all current events online, Republican National Committee officials told ABC News.
The leading Democratic presidential hopefuls also have changed their campaign plans. Sen. Bernie Sanders, I-Vt., will no longer hold large events or door-to-door canvases and will move to digital formats instead, according to his communications director, Mike Casca.
Former Vice President Joe Biden also will move to suspend large crowd events and move to virtual ones, according to his campaign.
The pandemic also has raised concerns about testing for the virus and who's eligible. Trump announced Friday he was declaring a national emergency "to unleash the full power of the federal government" and quickly get $50 billion to states, territories and localities "in our shared fight against this disease."
The "Happy Birthday" song is no longer reserved for your special day.
As the CDC urges everyone to wash their hands for at least 20 seconds, many have duly noted that you can sing the celebratory song twice to fill the time.
Americans also have been stocking up on hygiene products. Hand sanitizer sales spiked 73%, according to data from Nielsen covering a four-week period that ended Feb. 22, while sales of thermometers rose 47% and aerosol disinfectant purchases climbed 32%.
4. Public gatherings
The list of events canceled or suspended has grown exponentially in recent days.
From festivals to museums to sports seasons, organizers and executives are doing what they can to limit public gatherings. To see a full list of postponements and cancellations, click here.
In some cities, gatherings of a certain size have been either prohibited or urged against. In California, where a cluster of novel coronavirus cases were reported, Gov. Gavin Newsom said non-essential gatherings must be limited to no more than 250 people, while smaller events can proceed only if the organizers can implement social distancing of 6 feet per person.
"Changing our actions for a short period of time will save the life of one or more people you know," Newsom said in a statement.
The U.S. stock market has taken a major hit, with the Dow Jones Industrial Average seeing its biggest single-day decline -- almost 10% -- since one of more than 22% in 1987's Black Monday crash.
Though the markets saw a reprieve on Friday, a financial analyst told ABC News the public should expect to see continued volatility until the situation is under control.
"What's driving the sharp decline we've seen the market over the last three weeks is a health risk with a lot of unknowns," said Greg McBride, chief financial analyst at Bankrate. "Until we've got answers and we can model out what that means for the economy and corporate earnings, stocks are gonna be volatile."
Since Feb. 2, a Level 4 advisory, aka a Do Not Travel advisory, has been put in place for China. It's the strongest of the U.S. State Department's four travel warnings.
Other travel restrictions have followed.
Trump announced last week a ban on some travel from Europe to the United States for the next 30 days. The area Trump restricted is known as the Schengen zone and is made up of 26 countries including Italy, Spain, France and Germany. The ban was then extended to the U.K. and Ireland.
The State Department also issued a global health advisory, urging Americans to "Reconsider Travel" aboard.
"Many areas throughout the world are now experiencing COVID-19 outbreaks and taking action that may limit traveler mobility, including quarantines and border restrictions," the alert read. "Even countries, jurisdictions or areas where cases have not been reported may restrict travel without notice."
7. Stockpiling and price gouging
People have headed to grocery stores in droves, preparing to stock up and bear down.
Photos of empty aisles and lines out the door have circulated online, as a recent report showed that sales of several products on Amazon, namely sanitizers and medical face masks, rose at least 50% higher than their 90-day average after the World Health Organization declared an emergency.
Even products sold directly by Amazon, not third-party vendors, saw prices at least 50% since February, according to a report from the U.S. Public Interest Group.
"When people need something to stay healthy and prevent the spread of a potentially deadly virus, merchants should follow the Golden Rule, not the money,” Adam Garber, the group's education fund consumer watchdog, said in a statement.
8. Closed schools and offices
Numerous school districts and universities have postponed classes. Others have moved classes online. Students studying abroad were also asked to come home.
Major cities, including Boston, Miami, Chicago, Houston, San Diego and San Francisco, have closed schools for extended periods, with at least 21 million students impacted nationwide as of Friday night, according to Education Week.
For the working world, many companies have implemented telework policies.
As novel coronavirus continues to spread, so has anxiety.
Sales for medical face masks in the U.S. jumped 319% in the four-week period that ended on Feb. 22, according to Nielsen data.
But the CDC not only doesn't recommend that healthy people should wear masks, doctors have advised against it -- when putting on and taking off a mask, you're exposing your hands to your face.
Additionally, medical professionals need the masks to do their jobs, so shortages affect them significantly.
10. Fears and anxieties
With day-to-day life shifting rapidly, anxieties around the disease and the future have been heightened, according to Dr. Anne Maria Albano, a professor of medical psychology at Columbia University.
Albano said the public can either utilize that anxiety in a productive way or let it spiral.
"What people are experiencing is what anxiety in us is wired to do: Say, 'Hey, wake up and prepare for how to take care of yourself,'" she said. "Now the thing is, if the anxiety gets too high that then it becomes problematic, and this is what we want people to recognize. Anxiety, when it gets out of control, you are exaggerating what the risk to you and the people around you is."
She urged Americans to stay up to date with the CDC's preventative measures and best practices, as well reputable news outlets.
"I go on the subway in the morning. I wash my hands before I go on and I wash my hands when I go off," she said. "We have to learn how to balance what you're doing" to make sure you are informed but also limiting information that spreads on social media or inflammatory sites.