Aturbulent decade had reached its final day. It was New Year’s Eve 2019 and much of the world was preparing to celebrate.

The obituaries of the 2010s had dwelt on eruptions and waves that would shape the era ahead: Brexit, the Syrian civil war, refugee crises, social media proliferation, and nationalism roaring back to life. They were written too soon.

It was not until these last hours, before the toasts and countdowns had commenced, that the decade’s most consequential development of all broke the surface.

At 1.38pm on 31 December, a Chinese government website announced the detection of a “pneumonia of unknown cause” in the area surrounding the South China seafood wholesale market in Wuhan, an industrial city of 11 million people.

The outbreak was one of at least a dozen to be confirmed by the World Health Organization that December, including cases of Ebola in west Africa, measles in the Pacific and dengue fever in Afghanistan. Outside China, its discovery was barely noticed.

Over the next 100 days, the virus would freeze international travel, extinguish economic activity and confine half of humanity to their homes, infecting more than a million people and counting, including an Iranian vice-president, the actor Idris Elba, and the British prime minister. By the middle of April, more than 75,000 would be dead.

But all that was still unimaginable at the end of December, as 11.59pm ticked over to midnight, fireworks exploded and people embraced at parties and in packed streets.

Day 1

Wednesday 1 January
Wuhan seafood market shut down

The Wuhan seafood market is ordinarily bustling, but this morning police are weaving tape between its metal frames and hustling owners to shut their blue roller doors. Workers in hazmat suits carefully take samples from surfaces and place them in sealed plastic bags.

Concerned messages are circulating on Chinese social media, fuelled by medical documents that have found their way online warning that patients have been presenting at Wuhan hospitals with ominous symptoms.

“Sars is basically certain, don’t let the nurses go out,” one message says. Another says: “Wash your hands. Masks. Gloves”

Authorities in Taiwan are watching with alarm. The island is already implementing health precautions: arrivals on direct flights from Wuhan are being screened for flu-like symptoms on the tarmac in Taipei before they can disembark. Within two days, Singapore and Hong Kong will be monitoring arrivals from the city at their borders.

In Wuhan, eight people accused of spreading “rumours” about the disease are summoned to the Public Security Bureau. Another who will be reprimanded is a Wuhan ophthalmologist, Li Wenliang, for showing a group of his medical school alumni an analysis of the virus he believed was Sars.

Phrases such as “unknown Wuhan pneumonia” and “Wuhan seafood market” are already censored on YY, a popular livestreaming platform.

Day 9

Thursday 9 January
Novel coronavirus identified

The mystery disease is identified: Chinese scientists say the sick patients in Wuhan have contracted a previously undiscovered coronavirus.

Two coronaviruses, Sars and Middle Eastern Respiratory Syndrome (Mers), have already sparked pandemics this century. This new one is deadly too. Last night a 61-year old man died in a Wuhan hospital, the first known victim.

At this stage the official caseload is falling. Sequencing the virus has allowed doctors to strike off patients who were thought to be infected but who in fact only had ordinary pneumonia. No new coronavirus cases have been announced for four days.

The identification of the new virus is overshadowed by speculation over a plane crash on the outskirts of Tehran yesterday. Iran is blaming a technical fault but photos and videos circulating online are raising suspicions that it was shot down.

Later, a study will conclude that at this point the epidemic was doubling in size every week. Tomorrow Li Wenliang, the ophthalmologist, will start to show symptoms.

Day 13

Monday 13 January
Thailand reports first case

More than a week has passed since Wuhan health authorities last confirmed a case of the novel coronavirus. There has been nothing since the city began hosting an important annual meeting between state and provincial party officials.

But the virus has slipped the net. Thailand reports its first case, involving a 61-year old Wuhan resident whose high temperature was detected by a thermal surveillance scanner in Bangkok airport.

A committee of infectious disease specialists that goes by the acronym Nervtag meets in London to discuss the virus, and deems that the risk to the UK is “very low, but warrants investigation and testing”.

The Chinese government says there is not yet clear evidence of human-to-human transmission, including any signs of medical professionals becoming sick. The official message is echoed by the WHO, which issues a news release saying it is reassured of the quality of the Chinese government’s response.

Epidemiologists say the news is encouraging. “If there are no new cases in the next few days, the outbreak is over,” Guan Yi, a professor of infectious diseases at the University of Hong Kong, tells the New York Times.

Doctors in Wuhan are seeing a different picture. Studies will later show that for more than a fortnight, hospitals in the city have been dealing with “an exponential increase” in cases with no link to the seafood market.

Day 20

Monday 20 January
Human-to-human transmission confirmed

Zhong Nanshan, a trusted respiratory expert and the public face of the Chinese government response, goes on state television with bad news: two new cases of the virus have surfaced in Guangdong province among patients with no direct contact with Wuhan.

The conclusion is clear. “We can say it is certain that it is a human-to-human transmission phenomenon,” Zhong says.

Having seemed to vanish in China for more than a fortnight, the virus is now appearing across the country. On Friday night there were four new cases. By Sunday, 139. By the end of tomorrow, cases will have been confirmed in Beijing and Shanghai.

It is spreading around the world: Japan, South Korea, and the US, where yesterday a 35-year old man who had recently returned from Wuhan presented to a clinic in Washington state with a cough and a high fever, becoming the country’s first case.

Donald Trump received his first substantive briefing on the virus two days ago, during a session where he interrupted to ask when flavoured vaping products would return to the market, according to the Washington Post.

Panic is growing in Wuhan. At 6am, more than 100 patients with coronavirus symptoms were waiting to be seen at the city’s Xiehe hospital, a worker tells the Guardian.

24

Friday 24 January
Virus arrives in Europe

On the eve of the lunar new year holiday, as hundreds of millions of Chinese people are travelling to visit friends and family, Wuhan has in effect been sealed off. Most transport in and out of the city is suspended. More than 800 infections have been detected there and 25 people are dead.

The city is the first to experience the full glare of the outbreak: rapid increases in caseloads, hospitals under severe strain and an entire population quarantined.

The virus arrives in Europe, detected in two recent arrivals from China and a relative. The trio have had dozens of contacts and French authorities say they are racing to track down possible cases. “You have to treat an epidemic as you treat a fire,” says the French health minister, Agnès Buzyn.

Trump received his first media question about the virus while in Davos two days ago. Asked if he was concerned by a potential pandemic, he replied: “Not at all. And we have it perfectly under control.”

Tomorrow, China’s lockdown will be widened to include 56 million people. The president, Xi Jinping, will warn that the country is facing a “grave situation”. And Liang Wudong, a physician at the Xinhua hospital in Hubei, will become the first medical professional to die.

Day 31

Friday 31 January
Outbreak passes milestone on Brexit day

After nearly four years of agonising debate in parliament and across the country, at 11pm Britain formally exits the European Union. A virtual Big Ben beamed on to 10 Downing Street chimes for the milestone. Nearby, in Parliament Square, Nigel Farage leads a rendition of God Save the Queen.

It is also a milestone day for the coronavirus: by the end of day, the outbreak will be larger than Sars. It will be confirmed to have reached the UK. Spain and Italy will detect their first cases.

“The situation is serious but there is no need for alarm, everything is totally under control,” says the Italian health minister, Roberto Speranza.

Nobody has died outside China, but in China the death toll is accelerating, now at 258, with more than 11,000 infected. The US announces it is banning foreigners who have recently been in China from entering.

Day 36

Tuesday 4 February
First death outside China

The official case count in China passes 20,000, with 425 dead. A Wuhan resident who developed severe pneumonia last week dies in a hospital in Manila in the Philippines, the first person to succumb to the virus outside China. The Philippines bans any new arrivals from China.

The director general of the WHO says the disease’s international spread appears to be “minimal and slow”, though it could still worsen, and there is no need to unnecessarily halt trade and travel.

A London man arriving at Gatwick airport from Shanghai tells the Guardian he is alarmed at the lax approach there. He filled out a form detailing his contact information and onward travel plans but says it was ignored.

In Wuhan’s central hospital, Li Wenliang’s condition is worsening. His death in three days’ time will trigger howls of rage and grief in the locked-down city and across China.

The former directors of a White House pandemic preparedness office disbanded in 2018 publish an opinion piece in the Wall Street Journal. “Stop a US Coronavirus Outbreak Before It Starts,” the headline says.

Tomorrow the US Centers for Disease Control and Prevention will start distributing coronavirus testing kits across the country. But the devices are flawed, and over the next month the US will carry out just over 1,200 tests, while South Korea and Germany run at least 12,000 per day.

In a few days’ time, Trump will tell a rally in New Hampshire that the outbreak will soon ease. “By April, you know, in theory, when it gets a little warmer, it miraculously goes away,” he will say.

Day 50

Wednesday 19 February
Concerns over South Korea church

Rigorous testing and diligent contact tracing is paying off in South Korea, where just 30 cases of the virus have been recorded up to yesterday. But the 31st case, detected yesterday, is worrying authorities.

The woman, 61, belongs to a secretive megachurch and attended two services while ill. She ignored doctors’ initial requests that she be tested for coronavirus, instead going to lunch at a hotel buffet. Officials determine she has had at least 1,160 risky contacts. “After that, [the virus] just exploded,” Korea’s foreign minister, Kang Kyung-wha, will later say.

Iran announces its first two confirmed cases, both in the holy city of Qom.

In Milan, Atalanta continue their fairytale run in the Champions League, defeating the Spanish club Valencia 4-1, the stadium heaving with every goal. “Roughly a third of the population of the small town of Bergamo was present at the San Siro stadium,” a match report says. Thousands of Spaniards also made the journey to the capital of Lombardy province for the game.

In Las Vegas, the Democratic party holds its ninth presidential debate, the first to include the former New York governor Mike Bloomberg. It is dominated by searing attacks on Bloomberg’s reputation by the Massachusetts senator Elizabeth Warren. Coronavirus receives no mention.

Day 56

Tuesday 25 February
Virus takes hold globally

Global cases have exceeded 80,000. For the first time since the outbreak was announced, cases confirmed outside China outnumber those inside. On official numbers, Beijing reached the peak of its outbreak two days ago when 150 people died.

Others are just starting their climbs. Italy recorded its first death four days ago and now has 11 fatalities. About 50,000 people across northern Italy have been under lockdown for the past four days, the first population in Europe to be quarantined.

Iran’s death toll is believed to be largest outside China, with at least 12 fatalities confirmed officially and as many as 50 thought to have died in Qom alone, according to one lawmaker.

The disease is striking down the Islamic Republic’s elites: its deputy health minister appeared on television yesterday sweating profusely as he said the virus was under control. This afternoon, Iraj Harirchi confirms he has tested positive.

As the US announces its 14th case, Trump tweets during a state visit to India: “The coronavirus is very much under control in the USA. Stock Market starting to look very good to me!”
hotograph: Peter Byrne / PA Photograph: Ezra Acayan / Getty Imaotograph: Peter Byrne / PAPhotograph: Ezra Acayan / Getty Images

Day 66

Friday 6 March
Italy in crisis as UK records first death

Italy’s death toll has grown sixfold in six days: more than 230 Italians are dead and caseloads are growing by more than 1,200 every day. Rome has shut schools, banned spectators from Serie A football matches and is preparing to ringfence Lombardy.

“The health system risks going into overload and we will have a problem with intensive care if an exponential crisis continues,” says the prime minister, Giuseppe Conte.

A woman in her 70s becomes the first person to die from the virus in Britain, and Downing Street says the virus is now likely to spread “in a significant way”.

Three days ago, at a press conference, Boris Johnson raised eyebrows when he said he was continuing to shake hands. “I was at a hospital the other night where I think there were a few coronavirus patients and I shook hands with everybody,” he said.

Day 71

Wednesday 11 March
Covid-19 declared a pandemic

In a rare Oval Office address, Trump announces that his administration is embarking on “the most aggressive and comprehensive effort to confront a foreign virus in modern history”.

The number of cases in the US has passed 1,000 and more than 116,000 people are infected worldwide.

Stock markets in the US and UK are collapsing faster than at any time since the 2008 financial crash, panicked by the virus and a Saudi-Russian oil price war.

Deaths in Italy increase by 168 in a single day, the highest figure recorded anywhere. An image of an exhausted Italian nurse collapsed over her desk goes viral. The country is facing its “darkest hour”, Conte says.

The WHO declares what has become obvious: Covid-19 is a pandemic.

Britain has 456 cases but is resisting the kind of mass shutdowns being implemented elsewhere in Europe. Sick and vulnerable people are being advised to stay home, but the government is leaning towards the view that the cost of totally suppressing the virus will be too high in terms of lost liberties. Allowing its spread might also “build up some kind of herd immunity so more people are immune to this disease”, Sir Patrick Vallance, England’s chief scientific adviser, will later tell the BBC.

Day 77

Tuesday 17 March
Normal life on hold across world

European nations are sealing off from each other, and the continent is sealing off from the world. “We are at war,” the French president, Emmanuel Macron, declares.

Deaths in Italy are now exceeding 450 each day and will soon outnumber those in China. Confirmed cases in Spain will double to more than 17,000 by the end of the week. Three-quarters of those who have died from the disease are European.

Every hour is bringing new developments: more cases, more deaths and more restrictions on movement. Australians overseas receive an unprecedented request to return home as soon as possible. The French are banned from riding bikes. California’s 40 million residents are advised not to leave their homes.

Downing Street moves to urgently revise its strategy, including building herd immunity, after modelling lands on Boris Johnson’s desk showing that it might cost half a million British lives and send the NHS into meltdown.

In Burkina Faso, a former vice-president of the parliament dies from the virus, the first confirmed Covid-19 fatality in sub-Saharan Africa. By the end of the week there will be 1,000 cases on the continent. More than 160,000 cases have been confirmed around the world.

Day 83

Monday 23 March
Britain issues lockdown order

Confirmed cases around the world have exceeded 370,000, including more than 6,600 Britons. In what is thought to be one of the most-watched moments in British television history, Boris Johnson orders the closing of all non-essential businesses and urges the country: “You must stay at home.”

Nearly 400 die in Spain, its highest daily toll so far. It will prove to be the lowest toll for at least the next fortnight.

More than 5,000 new cases are confirmed in New York, bringing the state’s total to 20,000. By the end of the week the US will have the most infections in the world.

The wave appears to be receding in China, which this week recorded its first day with no cases of domestic transmission, including in Hubei, the province where the disease first appeared.

Tomorrow India’s prime minister, Narendra Modi, will urge his nation to “forget what going out means” for the next three weeks. The lockdown order will trigger one of the largest human migrations across the subcontinent since it was partitioned in 1947, as workers try to return to their home states. It means more than 3.5 billion people around the world are now living under some form of quarantine.

Day 93

Thursday 2 April
Another grim milestone passed

At around 8.40pm GMT, the Johns Hopkins University count of people confirmed to have Covid-19 passes 1 million, with more than 50,000 people dead. The sick include Boris Johnson, who says he is showing only minor symptoms and is still able to preside over the UK government’s response.

In Hungary, the prime minister, Viktor Orbán, has been granted the power to rule by decree with no time limit.

In India, a second case in discovered in Dharavi, a vast slum area in Mumbai and one of the most densely population places on Earth, fuelling fears that the country’s outbreak may be significantly worse than the official tally of 2,069 cases.

Deaths in Spain exceed 950 in a single day, the most yet recorded. Figures show a record 6.6 million Americans filed for unemployment benefits in the last week, in addition to the more than 3m who did so the previous week. The US has nearly a quarter of a million cases and 6,000 deaths. Field hospitals have been set up in New York’s Central Park, and refrigerated trucks are being used to store the dead. Trump warns of a “very, very painful two weeks” ahead.

Day 99

Wednesday 8 April
Future course of pandemic still unknown

Boris Johnson remains in hospital, having been admitted to intensive care on Monday after his symptoms worsened.

In some of Europe’s worst-hit countries, new transmissions and deaths are falling. China has recorded its first day with zero deaths and is cautiously reopening cities.

Last Saturday may have been the deadliest day so far, with more than 6,500 fatalities around the world. But with some of the poorest and most populous countries still officially relatively untouched by the virus, it is too early to say for sure.

Singapore, which was celebrated for its swift response, has introduced a strict quarantine amid signs of a possible second wave of infections. Vaccines are being fast-tracked but are unlikely to be in mass supply for at least 18 months.

Pakistan is reopening its construction sector. With a quarter of its population in poverty, the country is walking a tightrope between slowing down the virus and “ensuring people don’t die of hunger and our economy doesn’t collapse”, says the prime minister, Imran Khan.

A global total of more than 75,000 people are dead and 1.3 million have been infected. About 270,000 have recovered. There is no agreed-upon strategy on how to return life to normal.