The epidemic detective

Professor Dan Haydon is on the case. The epidemiologist who has research interests in agricultural diseases such as foot-and-mouth has recently been awarded a three year grant from the Biotechnology and Biological Sciences Research Council for his systems biology approach to understanding how these viruses spread.

Disease outbreaks are financially devastating. The 2001 UK outbreak of foot-and-mouth was estimated to cost in excess of £8 billion, while in France, the control of a disease that can cause the mass destruction of orchards - the plum pox virus - costs over €1.9m a year.

Most of the 2,026 infections during the foot-and-mouth outbreak in 2001 remain vaguely ascribed to “local spread”. ‘We want to know how those farms got it,’ says Professor Haydon. ‘We know that being next to an infected farm is a risk. But why did some farms become infected and not others? We don’t know the answer to these questions. And if we don’t know the answers, then how do we stop it next time?’

‘The type of work I do is very interdisciplinary. It is a mathematical exercise, it is a statistical exercise, it is a genetic exercise and it is an epidemiological exercise.’ Professor Dan Haydon

Professor Haydon’s approach utilises the fact that viruses are constantly mutating, making it possible to trace the path of infection during epidemics by sequencing viral genomes. ‘Basically if you had a cold and we sequenced the cold virus that you had, and then you gave it to a friend of yours and we sequenced the virus from them, we would probably be able to see small differences in the genome. If we then do this for lots of people in a cold outbreak, we could actually work out who had infected who. It leaves a genetic footprint if you like. This provides us with a means of tracing who infects who in disease outbreaks.’

Once this mapping has been done, the next step is to try and identify the factors that can account for why the virus has spread from one place to another. This might be anything from a stream connecting two farms, to one farmer visiting another during an outbreak. ‘It’s like detective work,’ Professor Haydon explains. ‘I call it epidemiological forensics. In a way, this is a fairly futuristic way of thinking about epidemiology. Now we can sequence the virus genome in real time during an epidemic, and use the information to guide our management of the epidemic. It also provides us with fundamental information about the transmission process, which is important for the future control of these devastating diseases.’