Analysing old data with new analysis methods may reveal the reasons for the spread of infectious diseases.
This was the topic of a recent workshop organised by the European Science Foundation (ESF), which called for the development of new mathematical and statistical tools to probe deeper into existing databases relating to human contact and pathogens.
Mirjam Kretzschmar, convenor of the ESF workshop, from the Medical Centre at Utrecht University in Holland, said: 'One of the most exciting conclusions we came to was the realisation that vast amounts of information were already available in various data banks.' These databanks hold information relating to the contact networks of people with various diseases, which could identify the pattern of transmission and the genotype (total genetic sequence) of the associated pathogens.
The ESF workshop highlighted the challenge involved in bringing this data together and drawing the correct conclusions from it.
Pathogens identified by their genotype, such as the influenza virus, can have different transmission patterns: some might spread faster and some might require closer contact between people to spread.
Therefore, correlating details of the unfolding contact networks between sufferers with the evolving genotype of the pathogen involved can yield valuable insights into the molecular factors relating to transmission.
Similarly, the disease may become more or less severe over time, or it may affect some types of people worse than others.
These factors can help identify what makes a pathogen dangerous and help with the future prediction of how a disease may spread.
This can lead to the development of a vaccine or public health recommendations, for example that certain high-risk individuals stay at home where possible.
Kretzschmar said: 'Research projects have shown that genotyping of pathogens can lead to insight into how risk networks are connected with each other and whether an outbreak consists of many small local outbreaks or whether we are dealing with a supra-national outbreak that requires different intervention strategies.' For example, the outbreak of LGV (lymphogranuloma venereum) among gay men in Europe during 2005 occurred in clusters and analysis showed that clusters from geographically distant cities were connected to each other.
Also, the analysis of genotypes showed that the outbreak was connected to earlier cases observed in San Francisco and had been going on for a long time.
This helped co-ordinate intervention activities among European countries.
The conference also heard how genotyping was helping to quickly identify emerging pathogens and their likely patterns of transmission.
For example, genotyping helped identify the insect-born virus Chikungunya and its transmission routes during a recent outbreak in Italy.
Such information can be correlated with contact tracing networks, which identify the transmission chains taken by an infection.
Kretzschmar said: 'Two types of contact tracing were discussed.
'One was the traditional way of asking infected persons who their contacts and possible sources of infection were and the other was tracing clusters of people with similar characteristics.' The latter type of contact network could be identified by taking people with similar genotypes and by considering people with similar types of risk behaviour that put them at risk: gay men already with specific types of high risk behaviour being an example for LGV.
Kretzschmar said: 'It shows that molecular typing can help uncover risk networks, especially if there is epidemiological information available that allows us to localise these networks and identify persons who are at risk but not yet infected.' The ESF workshop helped identify the types of data that could increase understanding of how infectious diseases spread and develop in populations.
It also identified the statistical and mathematical tools that could perform the required analysis.
The ESF workshop 'Mathematical Modelling to link Contact Network Analysis and Molecular Typing of Pathogens' was held in Utrecht, Holland, in November 2008.
