On the shores of the mighty Yangtze River, ancient temples meet towering skyscrapers and grim urban smogA kind of toxic fog caused by high levels of air pollution..

This is Wuhan, population 11 million and, normally, an unremarkable example of a 21st Century Chinese city. Unless you live there, you probably have not heard of it.

But today, normality is suspended in Wuhan. Somewhere among the hustle and bustle of this modern metropolisA very large and busy city. , seven people are lying critically ill with a mysterious illness. Health officials are asking: could this be the start of a new pandemicAn outbreak of disease which occurs across a wide geographic area, as opposed to an epidemic, which is confined to a particular region.?

At first, doctors in Wuhan were baffled when dozens of people began suddenly falling ill. Now, scientists have identified the infection as a type of coronavirusA family of viruses which are common throughout the world. Some cause only mild symptoms, such as a cold, but others can be deadly. Examples include Sars, Mers (Middle East Respiratory Syndrome) and Covid-19. , similar to SarsSevere Acute Respiratory Syndrome, a disease that makes it very difficult to breathe. Between 2002 and 2003, an outbreak of Sars in Southern China caused 774 deaths in 37 countries. It had a 9.6% fatality rate, and spread from civet cats to humans. , which killed 774 people between 2002 and 2003.

There is good reason to be worried. Viruses can be extremely deadly. During 1918 to 1919, the Spanish fluThe 1918 influenza pandemic (involving the H1N1 virus) infected an estimated 500 million people worldwide. Despite the name, Spanish flu is not thought to have originated in Spain. infected one-third of the world's population, killing 50 million people - more than in World War One.

It is now a race against time to stop the disease, transmitted from animals to humans, from spreading. But there is a problem: the source of the virus has not been identified. Most cases have been linked to a fish market in Wuhan, but it sells animals like bats and snakes too.

China, one of the most densely populated countries in the world, is the perfect place for a virus to spread. Even worse, centrally located Wuhan is a transport hub, with connections to Beijing and Hong Kong.

With Chinese New YearAlso known as the Lunar New Year or the Spring Festival, it is the most important date in the Chinese calendar. Celebrations last for up to 15 days. coming up, thousands will pass through the city, potentially taking the virus with them. On Monday, Thailand confirmed the first case outside of China.

But things may not be as bad as they first appear. Coronaviruses vary in severity. Most of the 59 infected people have recovered, and only one person has died.

No medical staff have been taken ill. This suggests that the virus is not spreading from human to human. This is good news.

Finally, precautions are in place to stop the illness from spreading. Officials are monitoring people, and taking passengers' temperatures on trains out of Wuhan. And for now, the seafood market is closed.

So, how worried should we be?

Very, say some. This virus, which causes lung problems, has started in the worst possible place - a huge city with worldwide transport links. It is not yet proven that the virus cannot be transmitted from human to human. The seafood market could be a false clue: scientists have not confirmed where the illness came from. We cannot protect ourselves because this is a new virus with no vaccineA biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, but in its weakest form..

Don't panic yet, say others. We may be overdue the next big pandemic - but this is not it. Since the seafood market was closed, few people have become ill. The virus does not appear to be that deadly - most recover after only a fever. Crucially, it does not appear to spread - like ebolaA highly infectious disease causing internal and external bleeding. A vaccine against it has recently been developed. - between people. With scientists monitoring the situation and taking precautions, the virus is unlikely to spread.

You decide

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What do we know? Since December 2019, over 50 people in the Chinese city of Wuhan have been taken ill with a virus that causes pneumonia. One person, who had underlying health conditions, has died and seven people are critically ill. Chinese and World Health Organisation officials have identified the infection as part of the coronavirus family. This makes the illness the seventh known coronavirus strain to affect humans. Authorities are clearly worried about panic - the hashtag #WuhanSARS is blocked on Weibo.

What do we not know? The animal species that the virus came from before passing to humans, and we do not know for certain where it happened. Although many cases have been linked to the South China Seafood Wholesale Market, it is not known if all of the patients had been there. We do not know if the virus will mutate and become more serious, and it has not been 100% proved that the virus cannot transmit between people. We simply cannot say at this stage if the virus will spread.