Contagion: Could it really happen?

Contagion - (c) Warner Bros
Image caption The film shows how panic and chaos spread

Hollywood blockbusters are not normally known for their scientific accuracy. So how realistic is the new disaster movie Contagion, which depicts the spread of a killer virus across the world?

'Too late to contain swine flu', 'Sars virus 'mutating rapidly', 'Bird flu fear as mutant strain hits China and Vietnam'.

These are not lines from the film. They are all real headlines from the past decade.

They all relate to illnesses which it was feared could spread around the globe and kill millions.

But, while each has claimed lives, none has become the feared "modern plague".

So how realistic is the depiction of the spread of the fatal infectious disease in Contagion?

According to one scientist who has already seen the film, the answer is very.

Prof John Edmunds, of the London School of Hygiene & Tropical Medicine, who looks at how best to tackle epidemics of disease, said: "It's obviously a worst-case scenario."

He added: "We can't rule it out as a possibility. And the science in the film was very good."

Likely candidates?

Contagion begins with Gwyneth Paltrow on a business trip in Hong Kong. It then shows how a virus she contracts spreads from person to person as she travels back home to the US and the chain of transmission begins.

Image caption Jennifer Ehle plays one of the scientists who tracks the virus

Prof Edmunds said it was possible to "quibble" about some of the scientific detail and the speed at which some things, like the development of a vaccine, happen in the film, which also stars Matt Damon, Jude Law, Kate Winslet and Jennifer Ehle.

But he added a great deal, such as the epidemiology - the investigation of the outbreak - and the involvement of the Center for Disease Control (CDC) was accurate.

"For example the 1918 flu pandemic was at least as severe as what's represented in Contagion.

"And in 2003 we had Sars (severe acute respiratory syndrome) - that was close to becoming a Contagion-like scenario.

"There were just two things that stopped it. People with Sars weren't infectious until they were showing symptoms, and by then they were in hospital. Also the hospitalisation and isolation provision was good."

But he said if those two things hadn't happened and the virus had spread more quickly and to places which didn't have the same healthcare systems, it would have been a different story.

And he said: "Aids is another example of a virus that has spread around the world. The only difference there is the mode of transmission."

When people think about viruses spreading around the world though, they tend to think of flu.

Bird flu - H5N1 - first appeared in 2003. Experts had been predicting that the world was due a major flu pandemic that would kill millions - and bird flu was seen as a likely candidate.

In the event, it has killed about 330 people since then, according to official statistics. But these were overwhelmingly people who farmed birds, or who had them in their own home.

At the moment it is self-defeating. It cannot spread easily between people because it kills its hosts quickly, thereby preventing its spread.

"Bird flu is extremely lethal," says Prof Edmunds. "About half the people with it have died. What has stopped it is it's not transmissible between humans, but it's not beyond the realms of possibility that it could become transmissible."

Where and when?

And then there was swine flu.

That first emerged in Mexico in 2009. It spread from country to country extremely quickly, because it was a new form of flu - H1N1 - that people did not have any resistance to.

By the end of February 2010, the pandemic had caused 15,921 deaths worldwide. However, by summer last year levels of the virus were falling and the World Health Organization (WHO) was able to declare the pandemic over.

But H1N1 was the prevalent strain of flu in the UK last winter, and it will be present again this year. It is different to most flus, in that it kills previously healthy adults. But for most, it is no worse than a normal flu.

It therefore has the capacity to spread like Contagion's virus, but isn't as likely to be fatal.

Image caption Gwyneth Paltrow is the first person affected

So, if Contagion depicts a possible, if worst-case, scenario, what's the most likely real-life candidate?

Well the scientists say it could be any of the things they know about, if they change or mutate in some way.

Prof Mike Catchpole, of the Health Protection Agency, said: "The one we watch particularly is flu. You only need to look back to the 1918 pandemic to see it can cause a huge number of cases - and a huge number of deaths.

"And we just don't know when or where the next pandemic flu will come along."

Or, perhaps more likely, the next global disease could be something that no-one has thought of yet.

More on this story

Related Internet links

The BBC is not responsible for the content of external Internet sites