A fast-moving virus known as the “new coronavirus” has infected thousands of Chinese citizens and spread to more than 20 countries.
The respiratory infection, which causes pneumonia-like symptoms, has claimed more than 900 lives so far – more than the 774 killed in the 2003 Sars epidemic.
The outbreak, originating in the Chinese city of Wuhan, has been declared a global emergency by the World Health Organization (WHO).
Here are 10 maps and graphics that will help you understand what is going on.
1. There have been thousands of cases – the majority in China
Across China, thousands of people have been infected with the coronavirus, with thousands more under medical observation.
The WHO has warned the number of cases is likely to rise further.
But while the overall number of cases continues to rise, the latest figures released by the Chinese National Health Commission show the number of new daily confirmed cases has begun to decline from a peak on 5 February.
The number of new cases in China is “stabilising”, the WHO says, but it is too early to say if the virus has peaked.
Head of the WHO’s health emergencies programme Dr Mike Ryan told a news conference the stabilisation “may reflect the impact of control measures put in place”.
But he warned against assuming the virus had plateaued.
Epidemics can slow down and then accelerate again, infectious disease experts say.
2. Daily deaths are rising
China has recorded its highest number of deaths in a single day from the new coronavirus, with 97 people dying on Sunday.
Figures released by the Chinese authorities show the number of daily deaths has risen steadily since the end of January.
The number of coronavirus cases and deaths have both overtaken that of the 2003 Sars epidemic, which also originated in China and killed 774 people.
There were around 8,100 cases of Sars – severe acute respiratory syndrome – reported during the eight-month outbreak.
3. China introduced a number of measures to try to halt the virus’s spread
Tight restrictions to contain the disease remain in place in China, despite some workers heading back to their jobs following an extended Lunar New Year holiday.
Authorities have cancelled flights, closed factories and schools and ordered some cities to go into lockdown in a bid to reduce infections.
Many companies are opening a selected number of workplaces as well as limiting staff numbers and staggering working hours.
Hubei province remains the worst affected, seeing by far the biggest number of cases of the virus as well as most of the deaths.
Its capital city of Wuhan, home to 11 million people, remains virtual lockdown, with its train stations and airports shut and its roads sealed.
The origins of the new coronavirus have been linked to illegally traded wildlife at Wuhan’s seafood market, which sells live animals including bats, rabbits and marmots. However, the exact source of the outbreak has not been identified.
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4. Two dozen countries have also had cases
The WHO declared the crisis a global health emergency on 30 January as a result of the virus’s spread outside China.
Infections have now been recorded in 25 countries including Japan, Thailand, the US, Canada, France, Germany and the UK. The majority of these cases are in people who had been to Wuhan.
In addition, 130 passengers out of a total of 3,700 have tested positive for the virus on a cruise ship quarantined in Japan.
But so far, there have been only two deaths outside mainland China – one in Hong Kong and one in the Philippines. Both men had been in Wuhan, the epicentre of the outbreak.
A growing number of countries have advised their citizens to avoid all non-essential travel to China and many have announced screening measures for passengers arriving from the country.
Some have also been evacuating their citizens from Wuhan and placing them in quarantine to monitor them for symptoms and avoid contagion.
The US has gone further and declared a public health emergency.
The UK government on Monday declared coronavirus a “serious and imminent threat” to public health, as it announced new powers to fight its spread.
The WHO has warned against closing borders, saying it would accelerate the spread of the virus if travellers started entering countries unofficially.
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5. The symptoms are respiratory
Coronaviruses are common, and typically cause mild respiratory conditions, such as a cough or runny nose.
But some are more serious – such as the deadly Sars and Mers – Middle East respiratory syndrome.
This outbreak – known as novel coronavirus (nCoV) – is a new strain that has not been previously identified in humans.
It seems to start with a fever, followed by a dry cough and then, after a week, leads to shortness of breath.
But in more severe cases, infection can cause pneumonia, severe acute respiratory syndrome, kidney failure and even death.
A report on the early stages of the outbreak by the Lancet medical journal said most patients who died from the virus had pre-existing conditions.
Medical researchers and scientists say it is too early to accurately predict how the virus will spread or calculate the death rate, partly due to mild cases remaining untested and unrecorded and a time lag of reporting infections.
There is not yet a specific anti-viral treatment for coronavirus, so people with the infection are currently being treated for their symptoms.
The existence of coronavirus was first flagged by a Chinese doctor in late December, but he was reprimanded by local police for “spreading rumours”.
Dr Li Wenliang, a 34-year-old ophthalmologist, has since died from the illness. His death was met with an intense outpouring of grief on Chinese social media as well as anger towards Chinese authorities.
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6. You can do things to reduce your chances of catching it
The WHO is advising people in affected areas to follow standard procedures to reduce the chance of catching the virus.
They include hand and respiratory hygiene as well as safe food practices.
People are advised to avoid close contact with people suffering from acute respiratory infections; wash hands regularly, especially after direct contact with ill people or their environment; and avoid unprotected contact with farm or wild animals.
Avoiding eating raw or undercooked animal products is also advised.
According to the WHO, although it may be possible that people with coronavirus may be infectious before showing significant symptoms, people showing symptoms are, so far, causing the majority of virus spread.
Those with symptoms should practise “cough etiquette”, including maintaining distance, covering coughs and sneezes with disposable tissues or the inside of an elbow, and washing hands.
In China, protective face masks are in widespread use – both among the general population and medical staff.
Although virologists are sceptical about their effectiveness against airborne viruses, there is some evidence to suggest the masks can help prevent hand-to-mouth transmissions.
Medical advice in China is to change masks regularly – as often as four times a day for medical teams – and Chinese authorities have appealed to other countries to help with supplies.
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7. If a case is suspected, there are processes to follow
The Chinese government has classified the outbreak in the same category as the Sars epidemic.
This means people diagnosed with the virus in the country must be isolated and can be placed in quarantine.
Within healthcare facilities, the WHO advises staff to implement enhanced standard infection prevention and control practices, especially in emergency departments.
The WHO advises that patients should be assessed quickly and treated for the level of severity of the disease they have – mild, moderate, or severe.
It also recommends immediately implementing infection prevention measures. These include staff wearing protective clothing and limiting patient movement around the hospital.
In the UK, the Department of Health has declared the new coronavirus as a “serious and imminent threat” to public health, giving authorities in England new powers to keep people in quarantine.
Arrowe Park Hospital, on the Wirral, and Kents Hill Park conference centre, in Milton Keynes, have been designated as “isolation” facilities in the UK.
Evacuees from Wuhan who travelled to the UK on two evacuation flights chartered by the Foreign Office are currently in quarantine at the locations.
By Dominic Bailey, David Brown, Mark Bryson, Ben Butcher, Lucy Rodgers, Irene de la Torre Arenas and Wesley Stephenson.