Health

Coronavirus: How worried should we be?

Wuhan Image copyright Getty Images
Image caption The outbreak occurred in the city of Wuhan, south of Beijing

A virus - previously unknown to science - is causing severe lung disease in China and has also been detected in other countries.

At least 41 people are known to have died from the virus, which appeared in the Chinese city of Wuhan in December.

There are already hundreds of confirmed cases, and experts expect the number will keep rising.

A new virus arriving on the scene, leaving patients with pneumonia, is always a worry and health officials around the world are on high alert.

But is this a brief here-today-gone-tomorrow outbreak, or the first sign of something far more dangerous?

What is this virus?

Officials in China have confirmed the cases are caused by a coronavirus.

These are a broad family of viruses, but only six (the new one would make it seven) are known to infect people.

Severe acute respiratory syndrome (Sars), which is caused by a coronavirus, killed 774 of the 8,098 people infected in an outbreak that started in China in 2002.

"There is a strong memory of Sars, that's where a lot of fear comes from, but we're a lot more prepared to deal with those types of diseases," says Dr Josie Golding, from the Wellcome Trust.

How severe are the symptoms?

It seems to start with a fever, followed by a dry cough and then, after a week, leads to shortness of breath and some patients needing hospital treatment.

Around one-in-four cases are thought to be severe.

The coronavirus family itself can cause symptoms ranging from a mild cold all the way through to death.

"When we see a new coronavirus, we want to know how severe are the symptoms. This is more than cold-like symptoms and that is a concern but it is not as severe as Sars," says Prof Mark Woolhouse, from the University of Edinburgh.

The World Health Organization (WHO) is considering declaring an international public health emergency - as it did with swine flu and Ebola.

How deadly is it?

Forty-one people are known to have died from the virus - but while the ratio of deaths to known cases appears low, the figures are unreliable.

But the infection seems to take a while to kill, so more of those patients may yet die.

And it is unclear how many unreported cases there are.

Where has it come from?

New viruses are detected all the time.

They jump from one species, where they went unnoticed, into humans.

"If we think about outbreaks in the past, if it is a new coronavirus, it will have come from an animal reservoir," says Prof Jonathan Ball, a virologist at the University of Nottingham.

Sars started off in bats and then infected the civet cat, which in turn passed it on to humans.

And Middle East respiratory syndrome (Mers), which has killed 858 out of the 2,494 recorded cases since it emerged in 2012, regularly makes the jump from the dromedary camel.

Which animal?

Once the animal reservoir (where the virus normally camps out) is detected, then the problem becomes much easier to deal with.

The coronavirus cases have been linked to the South China Seafood Wholesale Market, in Wuhan.

But while some sea-going mammals can carry coronaviruses (such as the Beluga whale), the market also has live wild animals, including chickens, bats, rabbits, snakes, which are more likely to be the source.

Researchers say the new virus is closely related to one found in Chinese horseshoe bats.

Why China?

Prof Woolhouse says it is because of the size and density of the population and close contact with animals harbouring viruses.

"No-one is surprised the next outbreak is in China or that part of the world," he says.

How easily does it spread between people?

At the beginning of the outbreak, the Chinese authorities said the virus was not spreading between people - but now, such cases have been identified.

Scientists have now revealed each infected person is passing the virus on to between 1.4 and 2.5 people.

This figure is called the virus' basic reproduction number - anything higher than 1 means it's self-sustaining.

We now know this is not a virus that will burn out on its own and disappear.

Only the decisions being made in China - including shutting down cities - can stop it spreading.

While those figures are early estimates, they put coronavirus in roughly the same league as Sars.

There are also concerns that people with no symptoms could be spreading the virus.

Prof Kwok-Yung Yuen from the University of Hong Kong-Shenzhen Hospital said "asymptomatic infection appears possible".

How often or easily this happens is far from clear, but it could make the virus far harder to contain.

How fast is it spreading?

It might appear as though cases have soared, from 40 to more than 800 in around a week. But this is misleading.

Most of the "new" cases were already out there but have only just been detected as China steps up its surveillance.

There is actually very little information on the "growth rate" of the outbreak.

But experts say the number of people becoming sick is likely to be far higher than the reported figures.

A report by the MRC Centre for Global Infectious Disease Analysis at Imperial College London said: "It is likely that the Wuhan outbreak of a novel coronavirus has caused substantially more cases of moderate or severe respiratory illness than currently reported."

While the outbreak is centred on Wuhan, there have been cases in Thailand, Japan, South Korea, Vietnam, France, Singapore, Taiwan, Nepal and the US.

Could the virus mutate?

Yes, you would expect viruses to mutate and evolve all the time. But what this means is harder to tell.

The novel coronavirus has jumped from one species to another. It could mutate to become easier to spread from one person to another or to have more severe symptoms.

This is something scientists will be watching closely.

How can the virus be stopped?

We now know the virus will not stop on its own; only the actions of the Chinese authorities can bring this epidemic to an end.

There is also no vaccine to give people immunity to the virus.

The only option is to prevent people who have become infected from spreading the virus to others.

That means:

  • Limiting people's movement
  • Encouraging hand-washing
  • Treating patients in isolation with healthcare workers wearing protective gear

A massive feat of detective work will also be needed to identify people whom patients have come into contact with to see if they have the virus.

How have Chinese authorities responded?

Image copyright Getty Images
Image caption Temperature screening can help identify people who have been infected

China has done something unprecedented anywhere in the world - by effectively putting Wuhan into quarantine.

Travel restrictions have also been imposed on a dozen other cities with 36 million people affected.

Some mass gatherings have been banned and tourists sites, including part of the Great Wall, have been closed.

Wuhan - the centre of the outbreak - is building a new hospital with a beds for 1,000 patients.

How is the world responding?

Most Asian countries have stepped up screenings of travellers from Wuhan and the WHO has warned hospitals worldwide a wider outbreak is possible.

Singapore and Hong Kong have been screening air passengers from Wuhan and authorities in the US and the UK have announced similar measures.

However, questions remain about the effectiveness of such measures.

If it takes five days for symptoms to appear, then someone could easily be halfway round the world and have passed through any screening checks before starting to feel ill.

How worried are the experts?

Dr Golding says: "At the moment, until we have more information, it's really hard to know how worried we should be.

"Until we have confirmation of the source, that's always going to make us uneasy."

Prof Ball says: "We should be worried about any virus that explores humans for the first time, because it's overcome the first major barrier.

"Once inside a [human] cell and replicating, it can start to generate mutations that could allow it to spread more efficiently and become more dangerous.

"You don't want to give the virus the opportunity."

Are there any vaccines or treatments?

No.

However, the work to develop them is already under way. It is hoped that research into developing a vaccine for Mers, which is also a coronavirus, will make this an easier job.