Epidemics: Scientists to hunt down new viruses before they strike

Scientists are preparing to hunt down the planet's last remaining viruses capable of triggering new diseases in humans. Several hundred new varieties may still be lurking in the wild or in remote populations, it is believed.

In recent years, deadly outbreaks of diseases such as Sars and Ebola have caused major health scares and officials are anxious to use modern gene-hunting technology to pinpoint pathogens before they can get a chance to spread through populations.

Among those backing the project is the company behind web search engine Google, which has launched a 'predict and prevent' programme aimed at setting up a network for forecasting emerging threats 'before they become local, regional, or global crises'.

'Some of these viruses have very limited impact but others can trigger pandemics,' said Dr Mark Woolhouse, of Edinburgh University's centre for infectious diseases. 'The purpose of this initiative is to identify viruses before they get a chance to spread among humans.' Woolhouse has been invited to work with the US National Academy of Sciences, which will hold a meeting next week aimed at drawing up plans to tackle the problem of emerging diseases.

'We are in the middle of a revolution in gene technology,' said Woolhouse. 'For the first time, we have the means to trace any pathogen that has infected a human or is capable of infecting a person.'

In recent years, biologists have developed chips that can identify every known human virus from blood or tissue samples and have designed machines that can unravel the genetic make-up of new organisms in minutes. As part of the virus-hunting programme, scientists would study remote populations and test individuals to detect previously unknown viruses in their blood. Other researchers would study animals in order to test if any carry viruses capable of infecting humans.

'Viruses infect men and women if they carry pieces of protein capable of unlocking receptors on the surfaces of human cells,' added Woolhouse. 'Testing animal viruses to see if they have protein sections that could easily mutate and open up our receptors would be one priority for the project.'

In a recent Royal Society paper, a team led by Woolhouse calculated that since 1960 an average of two to three new viruses affecting humans have been discovered every year. Most are transmitted to humans from other mammals. A smaller but significant number come from birds and wildfowl.

Recent examples include the 2002 outbreak of Sars virus, which killed hundreds of people, the Ebola virus - linked to fruit bats - which has caused several disease outbreaks since 1976, and the Sin Nombre virus, linked to the deer mouse, which caused deaths in the US in 1993.

As roads are built across Africa and South America, more people are encountering animals with which mankind has had little previous contact. In addition, pets have been linked to disease outbreaks, such as the Gambian pouched rat that was blamed for an outbreak of monkeypox in the US in 2003.

In other cases, changes in farming practices have triggered unexpected outbreaks. In Malaysia in 1999, more than 100 people died of a form of encephalitis that was traced to the Nipah virus. This outbreak was attributed to a decision by pig farmers to plant fruit trees on their land to boost income. Fruit bats, which were subsequently found to carry Nipah, came to the trees for food, dropped excrement on pigs below and the disease was then transmitted to humans.

However, the worst known outbreak caused by such viruses - known as zoonotic organisms - is the HIV/Aids epidemic. Tens of millions of people could die of the illness, which scientists believe was caused by a disease in chimps that was passed to humans in Cameroon in the Thirties. Pinpointing another HIV-like disease before it reaches humans is the key motivation for the new project.

Tuesday, December 2nd 2008

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