On December 31, 2019, the World Health Organisation’s (WHO) China office heard the first reports of a previously-unknown virus behind a number of pneumonia cases in Wuhan, a city in Eastern China with a population of over 11 million.
Since then the disease – formerly known as coronavirus but now called Covid-19 – has hit approximately 80,000 people in mainland China, killing 2,946. A further 10,566 cases and at least 166 deaths have been reported globally. The disease has been detected in at least 72 countries, with South Korea, Italy and Iran experiencing the most widespread outbreaks outside of China. In the UK, there have been 39 confirmed cases, although the UK health secretary Matt Hancock says that the country is still in the containment phase of the outbreak.
The Chinese government has responded to the outbreak by placing Wuhan and nearby cities under a de-facto quarantine encompassing roughly 50 million people in Hubei province. In northern Italy, authorities have placed 11 towns, mostly in the Lombardy region, on lockdown. Around 50,000 people cannot enter or leave towns in the area, with police patrolling the streets and fines in place to enforce the lockdown. South Korea, where more than 4,812 people have been infected, has placed itself on the highest level of alert to try and contain spread of the virus.
One of the worst Covid-19 outbreaks was on a cruise ship anchored off Japan. More than 705 people on board the Diamond Princess tested positive for the virus. The cruise liner was carrying more than 3,700 people, including 78 Britons, when it was quarantined in Yokohama on February 5.
On January 30, the WHO designated Covid-19 a "public health emergency of international concern" (PHEIC), indicating that international action will be required to contain the outbreak. In the past decade only five other PHEIC announcements have been made. On February 23, Chinese president President Xi Jinping described the Covid-19 outbreak as the "largest public health emergency" in the country's recent history.
A quick note on naming. Although popularly referred to as coronavirus, on February 11, the WHO announced the official name of the disease: Covid-19. The virus that causes that disease is likely to be called Severe Acute Respiratory Syndrome Coronavirus 2, or Sars-CoV-2 for short, according to a draft paper from the International Committee on the Taxonomy of Viruses.
How did Covid-19 start?
The disease appears to have originated from a Wuhan seafood market where wild animals, including marmots, birds, rabbits, bats and snakes, are traded illegally. Coronaviruses are known to jump from animals to humans, so it’s thought that the first people infected with the disease – a group primarily made up of stallholders from the seafood market – contracted it from contact with animals.
Although an initial analysis of the virus that causes Covid-19 suggested it was similar to viruses seen in snakes, the hunt for the animal source of Covid-19 is still on. A team of virologists at the Wuhan Institute for Virology released a detailed paper showing that the new coronaviruses' genetic makeup is 96 per cent identical to that of a coronavirus found in bats, while an as-yet unpublished study argues that genetic sequences of coronavirus in pangolins are 99 per cent similar to the human virus. Some early cases of Covid-19, however, appear to have inflicted people with no link to the Wuhan market at all, suggesting that the initial route of human infection may pre-date the market cases.
The Wuhan market was shut down for inspection and cleaning on January 1, but by then it appears that Covid-19 was already starting to spread beyond the market itself. On January 21, the WHO Western Pacific office said that the the disease was also being transmitted between humans – evidence of which is apparent after medical staff became infected with the virus. Since then, evidence of human-to-human transmission outside of China has been well established, making chances of containing the virus much harder.
What exactly is Covid-19?
Coronaviruses are a large group of viruses that are known to infect both humans and animals, and in humans causes respiratory illness that range from common colds to much more serious infections. The most well-known case of a coronavirus epidemic was Severe Acute Respiratory Syndrome (Sars), which, after first being detected in southern China in 2002, went on to affect 26 countries and resulted in more than 8,000 cases and 774 deaths. The number of people infected with Covid-19 has now well surpassed those hit with Sars.
While the cause of the current outbreak was initially unknown, on January 7 Chinese health authorities identified that it was caused by to a strain of coronavirus that hadn’t been encountered in humans before. Five days later the Chinese government shared the genetic sequence of the virus so that other countries could develop their own diagnostic kits. That virus is now called Sars-CoV-2.
Although symptoms of coronaviruses are often mild – including runny noses, headaches, coughs and fevers – in some cases they lead to more serious respiratory tract illness including pneumonia and bronchitis. These can be particularly dangerous in older patients, or people who have existing health conditions, and this appears to be the case with Covid-19. On February 5, Chinese health officials reported that two-thirds of the people who have died from Covid-19 were men, more than 80 per cent were over 60 years old and they typically had pre-existing health conditions such as diabetes or cardiovascular disease.
How far has it spread?
China has bore the brunt of Covid-19 infections (so far). As of March 2, Chinese health authorities had acknowledged over 79,968 cases and 2,873 deaths. Hubei province has been the hardest hit by Covid-19, with most of the infections occurring in Wuhan itself.
But in mid-February, the spread of the disease started picking up outside of China. Now there are confirmed cases in at least 72 countries. In the UK, the number of confirmed Covid-19 cases rose to 39 on March 4 after two more cases of the disease were discovered in Scotland.
In the rest of Europe, Italy has seen the highest number of cases. According to the WHO at least 52 people have died and there are more than 2,036 confirmed cases, mostly in the north of the country. In Lombardy, residents of towns hit with the disease have been confined to so-called "red-zones" where they are not permitted to leave.
South Korea has reported the most Covid-19 cases of any country outside of China. As of March 4, the country had reported 4,812 confirmed cases and 26 deaths. The majority of cases have been found in the southeastern city of Daegu and many of those hit with the disease are members of the Shincheonji Church, a secretive religious sect that has around 250,000 members in the country.
Iran, too, is seeing a surge in cases. The country has confirmed at least 66 deaths, which is more than in South Korea, a country that has seen three times as many cases. This suggests that the actual number of people with Covid-19 in Iran may be much higher than the 1,501 cases disclosed in the WHO's report on March 1. Many of cases are linked to Qom, a major Shiite religious centre and a city with more than one million residents.
What’s going to happen next?
WHO chief Tedros Adhanom Ghebreyesus has warned that the window of opportunity to contain Covid-19 is "narrowing". The WHO is still not declaring the outbreak a pandemic as its spread is broadly being contained, but recent outbreaks in Italy and Iran, which so far have no clear link to China, pose a significant challenge to health authorities trying to stop the spread of the virus.
After initially delaying the decision, on January 31, the WHO declared the Covid-19 outbreak an international public health emergency. The WHO cited the pace of the outbreak in China and cases of human-to-human transmission outside of the country among the factors contributing to the health agency's decision to declare an international emergency.
Since 2009 there have only been five declarations of international public health emergencies: the swine flu pandemic in 2009, a polio outbreak in 2014, the Western Africa Ebola outbreak in 2014, the Zika virus outbreak in 2015 and another Ebola outbreak in the Democratic Republic of the Congo in 2019.
The WHO's definition of pandemic is not as clear as its definition of a international public health emergency. The organisation defines a pandemic as a "worldwide spread of a new disease" – a criterion that Covid-19 seems to fulfil. But the agency has insisted that Covid-19 is not yet at pandemic levels, saying that there is still a window of opportunity to prevent the spread of the disease.
Matt Reynolds is WIRED's science editor. He tweets from @mattsreynolds1
Updated 04.03.20, 11:50 GMT: The article has been updated to reflect the latest figures about the spread of Covid-19. The original version of the article was published at 11:30 GMT on January 23, 2020.
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