How we could have stopped swine flu

Disease experts have long thought the world overdue for a new pandemic. Today, with the Mexican swine flu outbreak dominating the headlines, and despite improvements in disease surveillance systems, we are scarcely in a better position to identify new pandemics than we were when the deadly strains of influenza killed millions at the turn of the 19th century.

In the autumn of 1889, a lethal type of influenza swept across the Urals and into Russia, devastating St Petersburg and Moscow. No one saw it coming, and by the time the Russian influenza had burnt itself out, some 250,000 Europeans were dead. Nearly thirty years later, at the end of the first world war, another deadlier strain of influenza killed in excess of 50m people. This time the virus was blamed on Spain although, in truth, there is little hard evidence as to its origins. (Indeed, some epidemiological evidence suggests that the outbreak actually originated on pig farms in Kansas.) Again, no one saw it coming.



The next pandemic could be swine or bird flu, a new simian retrovirus (like HIV), or one of the deadly bat-borne viruses circulating in the jungles of southeast Asia. Indeed, 400 new viruses have emerged since the 1940s, many with no known cure. But since the 1970s, greater human encroachment on previously remote animal habitats means that the threat of novel animal pathogens, like swine flu, has increased. Other factors, including unsafe farming practices and global warming, may exacerbate this trend.

Prior to the current outbreak, the fright list was topped by three new new viruses: the H5N1 strain of bird flu; Nipah, a virus harboured by wild fruit bats that wiped out Malaysia's pig-breeding industry in 1999, killing 105 people in the process and which now appears to be endemic to rural areas of Bangladesh; and Hendra, another bat-borne virus which killed several racehorses and a vet at a Queensland stables in the summer of 2008.

In 1889 it took more than six months for the Russian influenza to spread around the world. Today, thanks to jet travel and rapid global trade connections, a pandemic strain of virus can spread around the world in a matter of days (as the current swine flu scare has demonstrated). Faced with the very real possibility of a fast-spreading global pandemic, the World Health Organisation (WHO) has responded by forging closer links with local organisations, like the Chinese Centers for Disease Control. But it has also begun to use sophisticated new software to trawl the internet for reports of unusual disease outbreaks.

This approach to spotting pandemics early has powerful backers. Last November, Google became the latest organisation to throw its weight behind the war on emerging infections diseases (EIDs) when it launched Google Flu Trends, a site which aims to predict annual winter flu outbreaks simply by tracking around 40 common terms people search for when suffering flu-like symptoms. (Google launched the site after its engineers found the results accurately tracked flu reports from doctors' surgeries and clinics, but without the normal one to two week reporting lag.)

Encouraged by the public reception to Flu Trends, Google is now seeking to go a stage further by launching other "predict and prevent" initiatives. One scheme already underway is Health Map, a site that searches for public information about disease outbreaks and uploads the data onto easy-to-read global maps. And in Cambodia, Google is hoping to trial a new scheme whereby villagers in remote rural areas will be able to use SMS technology to text information about disease outbreaks direct from their mobile phones. At a recent conference on EIDs in Vietnam, there was even talk of equipping mobile phones with built-in "virus" detectors that could monitor virus particles in people's breath whenever they spoke into the receiver.

But for all their ingenuity, the worry is that these amount to little more than technological tricks. One concern is that they can end up fueling the very anxieties they are supposed to alleviate. Google call this the "Angelina Jolie" effect—"If Angelina has diarrhoea you see a sudden spike in people searching for diarrhoea," admits Mark Smolinski, the head of Google's predict and prevent initiative. Equally, if people fear an outbreak of swine flu, and search for it out of worry, the tool becomes useless. But much more importantly, clever internet sites and search algorithms would have done little to spot a swine flu in Mexico, or many of the other less developed countries where viruses often begin, because few people use the internet. (The current best estimate suggests that the swine flu virus had been circulating in Mexico for a couple of weeks prior to being recognised, at least in part because the Mexican health system is poorly set up to spot emerging pandemics.) The problem with sites like Flu Trends, and similar technology-driven approaches, is that they are necessarily reactive.

What is needed is a fundamentally different approach, in which rather than waiting for the viruses to come to us, we go and find them first. This is the theory behind "deep viral mining"—essentially traveling to the jungles of Africa and Asia and gathering data on animal viruses before they leap the species barrier to humans. These techniques are the most reliable way to spot emerging threats. Such an approach in the early 1960s could have spotted the presumed precursor virus to HIV circulating in Africa, and in turn prevented the eruption of Aids in 1981. Similarly, if in the early 1990s the WHO had spent its money putting field epidemiologists on the ground in Guandong, the Chinese province where the SARS coronavirus likely first leaped from civet cats to humans, we may have be able to avoid the 2003 SARS epidemic.

Nathan Wolfe, a Stanford University biology professor and the director of the California-based Global Viral Forecasting Initiative, is one of the leading advocates of deep viral mining. His initiative aims to get "upstream" of viruses before they can spill over into human populations. In Wolfe's case this means spending half the year in Cameroon, monitoring bush meat hunters who venture into the jungle hunting gorillas and monkeys for food. The approach is laborious and expensive, but by taking blood samples both from hunters and villagers Wolfe has demonstrated that simian retroviruses continually circulate between apes and humans. He became the first scientist to demonstrate the transmission of the simian foamy virus, and is now looking at another common cross-over monkey virus, called HTLV.

Wolfe has similar projects underway in the Congo, Laos and Madagascar. Meanwhile, in Malaysia, the Henipavirus Ecology Collaborative Research Group—HERG for short—is conducting similar research involving Malaysian flying foxes, the bats that transmit Hendra, while in Bangladesh the Consortium for Conservation Medicine and the Wildlife Trust has been conducting field trials with villagers who are regularly infected with Nipah, possibly as a result of the bats feeding on trees that provide the villagers with syrup.

Viral mining will do nothing to stop an outbreak like swine flu once it is spreading in the west. But it could stop the next threat. One obvious place to start would be the live animal markets where Asians shop for chickens, ducks and more exotic fare. The mutations in civet cats that sparked SARS, for instance, probably occurred in just such a market, and live poultry markets have also been implicated in a number of recent infections with the bird flu virus, H5N1. The good news is that governments like the Chinese are at last beginning to take the collection of viral and immunological data seriously, and share it with western scientists, which means that if H5N1 does mutate into a pandemic virus we will know about it quickly. The trick in the future will be to ensure to that other governments, including the Mexican one, do the same. Meanwhile pandemic watchers at WHO should spend more time looking for diseases in the jungle, and less on the internet. Otherwise, when the next pandemics comes, we'll be no wiser than our Edwardian forebears.