Timeline: How coronavirus got started

The outbreak spanning the globe began in December, in Wuhan, China.

The novel coronavirus outbreak, which began in Wuhan, China, in December, has expanded to touch nearly every corner of the globe. Hundreds of thousands of people around the world have been sickened and thousands of others have died.

The World Health Organization has declared the virus a global health emergency and rated COVID-19's global risk of spread and impact as "very high," the most serious designation the organization gives.

Here's a timeline of how the outbreak has unfolded so far:

Dec. 31, 2019: WHO says mysterious pneumonia sickening dozens in China

Health authorities in China confirm that dozens of people in Wuhan, China, are being treated for pneumonia from an unknown source. Many of those sickened had visited a live animal market in Wuhan, but authorities say there is no evidence of the virus spreading from person to person.

Jan. 11, 2020: China reports 1st novel coronavirus death

Chinese state media reports the first death from novel coronavirus, a 61-year-old man who had visited the live animal market in Wuhan.

Jan. 21, 2020: 1st confirmed case in the United States

A man in his 30s from Washington state, who traveled to Wuhan, is diagnosed with novel coronavirus. Japan, South Korea and Thailand also report their first cases one day prior.

Jan. 23, 2020: China imposes strict lockdown in Wuhan

China imposes aggressive containment measures in Wuhan, the epicenter of the outbreak, suspending flights and trains and shutting down subways, buses and ferries in an attempt to stem the spread of the virus.

Jan. 30, 2020: WHO declares global health emergency

For the sixth time in history, the World Health Organization declares a "public health emergency of international concern," a designation reserved for extraordinary events that threaten to spread internationally.

Feb. 5, 2020: Diamond Princess cruise ship quarantined

More than 3,600 passengers are quarantined on a cruise ship off the coast of Yokohama, Japan, while passengers and crew undergo health screenings. The number of confirmed cases on board the ship would eventually swell to more than 700, making it one of the largest outbreaks outside of China.

Feb. 11, 2020: Novel coronavirus renamed COVID-19

The WHO announces that novel coronavirus' formal new name is COVID-19. "Co" stands for coronavirus, "Vi" is for virus and "D" is for disease. Health officials purposely avoid naming COVID-19 after a geographical location, animal or group of people, so as not to stigmatize people or places.

Feb. 26, 2020: 1st case of suspected local transmission in United States

The Centers for Disease Control and Prevention (CDC) confirms the first case of COVID-19 in a patient in California with no travel history to an outbreak area nor contact with anyone diagnosed with the virus. It's suspected to be the first instance of local transmission in the United States. Oregon, Washington and New York soon report their own cases of possible community transmission.

Feb. 29, 2020: 1st death reported in United States

The first COVID-19 death is reported in Washington state, after a man with no travel history to China dies on Feb. 28 at Evergreen Health Medical Center in Kirkland, Washington.

Two deaths that occurred Feb. 26 at a nearby nursing home would later be recorded as the first COVID-19 deaths to occur in the United States. Later still, a death in Santa Clara, California, on Feb. 6 would be deemed the country's first COVID-19 fatality after an April autopsy.

March 3, 2020: CDC lifts restrictions for virus testing

The CDC issues new guidance that allows anyone to be tested for the virus without restriction. Previously, only those who had traveled to an outbreak area, who had close contact with people diagnosed with COVID-19, or those with severe symptoms, could get tested.

March 13, 2020: Trump declares national emergency

President Donald Trump declares a U.S. national emergency, which he says will open up $50 billion in federal funding to fight COVID-19.

March 15, 2020: CDC warns against large gatherings

The CDC warns against holding or attending gatherings larger than 50 people, including conferences, festivals, parades, concerts, sporting events and weddings for eight weeks, recommending that individuals cancel or postpone those events to avoid spreading the virus or introducing it into new communities.

March 17, 2020: Coronavirus now present in all 50 states

West Virginia reports its first COVID-19 case, meaning the disease is present in all 50 states.

March 17, 2020: Northern Californians ordered to 'shelter in place'

Six countries in the San Francisco area ordered to "shelter in place" for three weeks, meaning residents are required to remain at home unless they are leaving the house for an essential reason, or are exercising outdoors.

March 18, 2020: China reports no new local infections

China reports no new domestic infections in the country for the first time since the outbreak began. If the trend holds for 14 days, it could be a sign that China's outbreak is ending. The country is still seeing travel-related COVID-19 cases and it remains to be seen whether China will be able to prevent a second wave of infection, once the government's strict lockdown measures are lifted.

March 19, 2020: Italy's death toll surpasses China's

Italy's death toll tops 4,000, making it the first country to report more overall deaths than China, despite its much smaller population. The following week, COVID-19 deaths in Spain would similarly eclipse deaths in China.

March 20, 2020: New York City declared US outbreak epicenter

New York City state reports that more than 15,000 people have tested positive for COVID-19 and account for roughly half of the infections in the country. The vast majority of New Yorkers with COVID-19 are in the New York City region, which Mayor Bill de Blasio calls the "the epicenter of this crisis," warning that the outbreak will get worse as supplies dwindle.

March 24, 2020: Japan postpones Olympics

Japan postpones the 2020 Summer Olympics, which were originally slated to be held in Tokyo starting July 24, until summer 2021. Countries including Canada and Australia had already announced that given the public health risk of the COVID-19 pandemic, they would not be sending their athletes to the Games.

March 24, 2020: India announces 21-day complete lockdown

Indian Prime Minister Narendra Modi announces a total ban on the country's 1.3 billion citizens leaving their homes for 21 days, in order to stop the spread of COVID-19.

March 26, 2020: United States leads the world in COVID-19 cases

The United States now has more confirmed coronavirus cases than any other country in the world, with cases topping 82,000 and deaths topping 1,000.

March 27, 2020: Trump signs $2 trillion stimulus bill

President Donald Trump signs a $2 trillion coronavirus relief bill into law. The law guarantees loans to small businesses and creates a lending system for distressed companies. It also provides financial aid to hospitals on the frontlines of the crisis.

March 27, 2020: UK Prime Minister Boris Johnson tests positive

Boris Johnson, the prime minister of the United Kingdom, tests positive for COVID-19 after having a high fever and persistent cough. Johnson will continue to lead the government via video conferences.

April 2, 2020: Global cases hit 1 million

More than 1 million people around the world have been diagnosed with COVID-19. Given testing shortages, undiagnosed cases and suspicions about governments obscuring the scope of their respective outbreaks, the actual number of people sickened is believed to be much higher.

April 9, 2020: Evidence that first COVID-19 cases in NYC came from Europe

A new study finds evidence that the first COVID-19 cases in New York City originated in Europe and occurred as early as February. Researchers traced the origin of New York City's outbreak and found it was primarily linked to untracked transmission between the U.S. and Europe, with limited evidence showing direct introductions from China or other countries in Asia.

April 21, 2020: Autopsy revels 1st US COVID-19 death was earlier than previously thought

The CDC confirms that tissue from an individual in Santa County, California, who died Feb. 6 tested positive for COVID-19 . That death occurred weeks earlier than the COVID-19 deaths in the Seattle area Feb. 26 that were previously believe to be the nation's first.