What is coronavirus and how close is it to becoming a pandemic?

More than 69,000 have been infected with a novel virus that originated in a Chinese seafood market, with nine confirmed cases in the UK

4 hours ago
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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 77,150 people in mainland China, killing 2,592. A further 2,246 cases and 31 deaths reported globally. On February 24, it was reported that 50 people had died from Covid-19 in the Iranian city of Qom. The Iranian government has disputed this figure.

The total death toll from Covid-19 has exceeded that of the Sars outbreak in 2002 and 2003 with health officials now warning that we are on the brink of Covid-19 going from an epidemic to a pandemic. Significant outbreaks in Iran, Italy and South Korea are of particular concern, with authorities struggling to find the “patient zero” to help explain where the outbreak came from.

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 600 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 620 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. Many of those aboard have been airlifted back to their home countries but the ship remains under lockdown.

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. Cases in Taiwan, Thailand, Germany, Vietnam, Japan, Franc, the UK and the United States also involved patients who had not been to China, implying that there has been some human-to-human transmission outside of China.

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 February 24, Chinese health authorities had acknowledged over 77,150 cases and 2,592 deaths. Hubei Province has been the hardest hit by Covid-19, with most of the infections occurring in Wuhan itself.

The list of other countries that have confirmed infections includes Hong Kong, Macao, Japan, South Korea, Italy, Singapore, Iran, the US, Thailand, Taiwan, Australia, Malaysia, Vietnam, France, the United Arab Emirates, the United Kingdom, Canada, Philippines, Kuwait, India, Russia, Spain, Lebanon, Israel, Belgium, Nepal, Sri Lanka, Sweden, Cambodia, Finland and Egypt.

In the UK, the first two Covid-19 cases were confirmed on January 31. The infected people were from the same family and were taken ill while staying at a hotel in York. By February 24 the number of people confirmed with Covid-19 in the UK had risen to 13 – with four of the new cases all being traced back to a single confirmed UK case. On February 15, when there were nine confirmed cases in the UK, NHS England confirmed that eight of those patients had been discharged from hospital. Eighty-three Britons who were held in quarantine after being evacuated from Wuhan were released on February 13 after everyone tested negative for the virus.

In the US, the Centres for Disease Control and Prevention has recommended against all nonessential trips to China, while the UK Foreign and Commonwealth Office is advising against all travel to Hubei Province and all but essential travel to the rest of mainland China.

On January 31, US health secretary Alex Azar said that foreign nationals who had travelled in China in the past 14 days would not be allowed entry to the US. New Zealand is also denying entry to foreign nationals or non-residents who are travelling to the country from mainland China or after transiting through China.

Russia, meanwhile, closed its border with China in an effort to contain the spread of the virus. On January 30, prime minister Mikhail Mishustin said the border closure would be one part of a number of measures to prevent Covid-19 spreading in Russia. Following news of an outbreak in Iran, Turkey, Pakistan and Armenia have all closed their land borders with the country.

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.

Matt Reynolds is WIRED's science editor. He tweets from @mattsreynolds1

Updated 24.02.20, 11:30 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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