Since then, close to 28 million Americans have been infected with the novel (new) coronavirus, officially known as SARS-CoV-2, according to the latest data from Johns Hopkins University. Nearly half a million have died, more than in any other country in the world. The year has been one of unspeakable tragedy, but also hope with the arrival of the first COVID-19 vaccines. The development of these highly effective vaccines is “a great scientific tour de force,” according to Thomas Russo, MD, chief of infectious disease at the University of Buffalo Jacobs School of Medicine and Biomedical Sciences in New York. Here’s a look back at the most significant U.S. milestones in the pandemic’s first year, where we stand now, and the challenges ahead.

December 31, 2019: In China, the Wuhan Municipal Health Commission Reports the First Clusters of Pneumonia-Like Illness

Local authorities are able to report that some patients work at the Huanan Seafood market. Later, the WHO will identify the Huanan market — a “wet” market that sells live animals — as the source of the coronavirus.

January 21, 2020: The CDC Confirms the First Case of COVID-19 in the United States

A 35-year-old man living in Washington state is the first in the United States to test positive for the coronavirus six days after his return from Wuhan, says the CDC. Health officials in the United States still don’t have much information regarding how the virus spreads, and the general consensus is that it likely moves from animals to humans, with very limited human-to-human transmission.

January 22, 2020: The WHO Announces Evidence of Human-to-Human Transmission

During a field visit to China, WHO officials determine that the coronavirus can spread between people.

February 1, 2020: First Case of COVID-19 Identified in a Diamond Princess Cruise Ship Passenger

February 5, 2020: The CDC Sends Out COVID-19 Testing Kits Later Revealed to Be Defective

After a sluggish start, the CDC begins to roll out coronavirus testing kits to state and local labs — tests that are soon revealed to be faulty. Problems with testing will become a hallmark of the U.S. pandemic response.

February 11, 2020: The WHO Officially Names the Virus

As infections spread in the United States largely undetected, the WHO gives the virus a name — severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 for short) and assigns the name COVID-19 to the disease it causes.

February 20, 2020: The CDC Announces the First COVID-19 Death in the United States

Health officials declare that a Washington state man in his fifties is the first in the country to die of COVID-19. The CDC reports the man’s death, as well as another first: A healthcare worker at a long-term care facility in the same state is diagnosed with COVID-19 and hospitalized. A resident of the facility also contracts the virus and is hospitalized. Washington will soon becomes the first COVID-19 hotspot in the United States. Retroactive studies will later reveal that two people in California died of COVID-19 weeks before, on February 6 and 17.

February 27, 2020: Trump Equates COVID-19 to the Flu

“This is a flu. This is like a flu,” says the President in a press briefing, as recounted by Fox News. “It’s a little like a regular flu that we have flu shots for. And we’ll essentially have a flu shot for this in a fairly quick manner.”

March 5, 2020: Grand Princess Cruise Ship Docked off San Francisco Begins COVID-19 Quarantine

Following the death of an elderly man who tested positive for the coronavirus after returning home from a Grand Princess cruise, 2,422 passengers are quarantined in their staterooms by order of the CDC. On March 6, President Trump says he wants those on board the Grand Princess to stay on the ship so they won’t be counted as American cases. “I like the numbers being where they are. I don’t need to have the numbers double because of one ship that wasn’t our fault,” Trump says.

March 11, 2020: The WHO Designates COVID-19 as a Pandemic

The WHO puts the COVID-19 toll at 118,000 cases and 4,291 deaths in 114 countries. “In the past two weeks, the number of cases of COVID-19 outside China has increased 13-fold, and the number of affected countries has tripled,” says WHO director-general Tedros Adhanom Ghebreyesus, PhD, in a briefing. Dr. Tedros says he hopes the pandemic designation will prompt countries to implement more drastic measures to protect against COVID-19, and help countries with fewer resources. “Several countries have demonstrated that this virus can be suppressed and controlled. The challenge for many countries who are now dealing with large clusters or community transmission is not whether they can do the same — it’s whether they will,” he says.

March 11, 2020: Tom Hanks Announces That He and His Wife, Rita Wilson, Have COVID-19

March 13, 2020: Trump Declares a National Emergency

As part of this announcement, Trump issues a ruling blocking non-U.S. citizens from entering the country if they have been in areas that are experiencing COVID-19 outbreaks, including China, Iran, and 26 European countries. The order allows the government to unlock billions of dollars in federal aid to help state and local governments with their COVID-19 response.

March 14, 2020: Anti-Asian Sentiment in the United States Leads to an Act of Shocking Violence

Trump repeatedly calls the coronavirus the “China virus,” helping inflame anti-Asian sentiment in the United States On March 14, members of a family from Myanmar, including a 2-year-old girl and 6-year-old boy, are stabbed outside a grocery store in Midland, Texas, by someone who thought they were Chinese and believed they were infecting people with the coronavirus, according to an FBI report obtained by ABC News.

March 19, 2020: California Is the First State to Issue a Stay-at-Home Order

California governor Gavin Newsom orders residents of the state to leave home only for necessities. During the next two months, 42 states and territories will implement restrictions.

March 23, 2020: New York City Cases Spike

March 26, 2020: The U.S. Becomes the Global COVID-19 Epicenter

By the end of March, the U.S. has more COVID-19 cases and deaths than any other country. The CDC counts over 81,000 cases and 1,000 deaths, more than in early epicenters including China and Italy, according to data gathered by The New York Times.

March 28, 2020: The FDA Authorizes Hydroxychloroquine for Emergency Use in COVID-19 Patients

April 3, 2020: The CDC Urges Americans to Wear Masks in Public

Until April, the CDC discouraged people without COVID-19 symptoms from wearing face coverings, largely in an effort to reserve the limited supply of N95s and surgical masks for healthcare workers. But the agency changes its stance as evidence mounts that infected people without symptoms can transmit the virus. Americans take to their sewing machines to churn out cloth masks even as shortages of medical-grade masks and other PPE (personal protective equipment) endanger healthcare workers. RELATED: The Latest Intel on Masks and the Coronavirus

May 15, 2020: Trump (Flanked by Drs. Fauci and Birx) Announces Operation Warp Speed

May 29, 2020: The United States Withdraws Funding to the WHO

Trump announces that the United States will sever its relationship with the WHO. He says the decision is based on the WHO’s reluctance to take a tough stance against China, which he believes has not been forthcoming about sharing COVID-19 information.

June 26, 2020: White House Coronavirus Task Force Addresses Rising Cases in the American South

Vice President Mike Pence and White House coronavirus response coordinator Deborah Birx, MD, speak on behalf of the U.S.’s Coronavirus Task Force as cases spike in Texas, Arizona, Florida, Mississippi, South Carolina, Alabama, Georgia, Louisiana, Nevada, and Utah, driven by young adults who are spreading the virus at social gatherings.

July 9, 2020: The WHO Announces That COVID-19 May Be Airborne

The announcement comes three days after a group of scientists publish an open letter in the journal Clinical Infectious Diseases, urging public health officials to acknowledge that the virus likely can spread through the air. “Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are released during exhalation, talking, and coughing in microdroplets small enough to remain aloft in air and pose a risk of exposure at distances beyond 1 to 2 meters from an infected individual,” the letter reads. Previously, public health experts had focused on virus spread through respiratory droplets or direct contact with a contagious person or contaminated surfaces. RELATED: To Reduce COVID-19 Risk, Open a Window

August 7, 2020: Sturgis Motorcycle Rally Becomes Superspreader Event

September 26, 2020: White House Rose Garden Event for Judge Amy Coney Barrett Become Likely Superspreader Event

Around 150 people gather in the Rose Garden for a ceremony at which President Trump nominates judge Amy Coney Barrett for the Supreme Court, followed by an indoor reception. Numerous guests — including former New Jersey governor Chris Christie, former counselor to the president Kellyanne Conway, and Senators Mike Lee of Utah, and Thom Tillis of North Carolina — test positive for COVID-19 within days. RELATED: Superspreaders: Could You Unknowingly Infect Hundreds — or Thousands — of Other People With the Coronavirus?

October 2, 2020: Trump Leaves White House via Helicopter to Be Hospitalized for COVID-19

October 22, 2020: The FDA Approves First COVID-19 Drug

The FDA approves the antiviral drug Veklury (remdesivir) for the treatment of hospitalized COVID-19 patients. RELATED: What You Need to Know About Remdesivir, the First FDA-Approved Treatment for COVID-19

November 4, 2020: The United States Reports 100,000 Cases in 1 Day for the First Time

Missouri, Alaska, Ohio, Iowa, Indiana, Minnesota, Nebraska, North Dakota, and New Mexico all reach record seven-day averages for cases and hospitalizations, according to CNBC. By mid-November, North Dakota has the highest rate of cases per capita in the world, followed by South Dakota.

November 9, 2020: The FDA Authorizes First Monoclonal Antibody Treatment for Emergency Use

The experimental drug bamlanivimab is a treatment for mild to moderate COVID-19 in adults and children over age 12 who are at high risk for progressing to severe COVID-19 and hospitalization. Monoclonal antibodies are made in the lab to mimic proteins that the body produces naturally as part of its immune response.

December 11 and 18, 2020: The FDA Authorizes First COVID-19 Vaccines for Emergency Use

RELATED: What You Need to Know About the COVID Vaccine

January 6, 2021: Colorado Documents First U.S. Case of U.K. Coronavirus Variant

The result of viral mutations, this variant is more highly contagious. Since Colorado documented the first cases of B.1.1.7 in the United States in early January, it has been identified in more than 500 cases in 33 states. On January 25, a Minnesota Department of Health lab confirms the first U.S. case of the P.1 variant, which originated in Brazil. Three days later, South Carolina documents the first case of B.1.351, the variant from South Africa. RELATED: Should You Double Mask? Plus 7 More Ways to Thwart the New Coronavirus Variants

January 19, 2021: Johnson & Johnson Announces Safety and Efficacy Data for Its COVID-19 Vaccine

The single-dose Johnson & Johnson vaccine is expected to receive FDA emergency use authorization in early March. While it is 66 percent effective at preventing moderate to severe COVID-19, it appears to eliminate the risk of hospitalization and death. “In a vacuum, the Johnson & Johnson data looks tremendous. It will still have a very important role in bringing this pandemic to an end,” says the University of Buffalo’s Dr. Russo.

February 2, 2021: Number of Americans Who Have Received a COVID-19 Vaccine Surpasses Total Number of Cases in the United States

February 9, 2021: The FDA Authorizes New Monoclonal Antibody Combination Treatment for Emergency Use

The government agency greenlights a combination of two monoclonal antibody drugs — bamlanivimab and etesevimab — for the treatment of mild to moderate COVID-19 in patients aged 12 and up who are high risk for progressing to severe COVID-19 or hospitalization. Researchers hope this combo therapy will give doctors another weapon in the fight against new coronavirus variants.

February 20, 2021: U.S. Marks a COVID-19 Anniversary

In the year since the CDC announced the first U.S. death from COVID-19, scientists have fundamentally changed their view of the disease. “It’s not just a respiratory virus like we had originally thought. Virtually every organ in the body is affected because the virus causes inflammation and disrupts blood vessels,” says Russo. “Currently, we are looking at who is hospitalized and dying and who is not, but I don’t think that’s the end of the story.” RELATED: Brain Fog: A COVID-19 Symptom That May Linger