New research shows how 'genetic fingerprinting' can be used to track the spread of STDs

New research shows it could be possible to follow the spread of bacterial sexually transmitted diseases (STDs) through the population by tracking the individuals in a city infected with the same strain of the bacterium. This could help provide better information to public health workers, allowing them to develop more effective public health campaigns.

The research published in The Lancet shows how the team used molecular typing or genetic fingerprinting to identify the gonorrhoea strains infecting individuals in London. They found the typing identified a number of common strains which appear to identify individuals in the major sexual networks in London.

Professor Brian Spratt, from Imperial College London, and senior author of the paper said: "Gonorrhoea is a good indicator of unsafe sex but most infections don't spread much and most strains in London are only found in one or a few individuals. However, occasionally a strain gets into a group of individuals with high rates of partner exchange and it can then spread rapidly and cause an outbreak or become endemic. Our approach can identify these major strains and the individuals infected with them, who are at increased risk of acquiring other STDs, including HIV/AIDS."

The researchers from Imperial College London and the Health Protection Agency used molecular typing to analyse different strains of gonorrhoea. Out of a total of 2045 strains recovered in London during a six month period, they were able to identify 21 prevalent strains, each infecting between 20 and 124 individuals. Seven of these strains were almost exclusively from homosexual men, while the other 14 were from almost exclusively from heterosexuals, suggesting very little spread of gonorrhoea between different behavioural groups.

Professor Catherine Ison, from the Health Protection Agency, and one of the paper's authors, added: "The creation of more highly targeted public health interventions could be of enormous value. Particular strains of gonorrhoea can become concentrated in certain groups if enough people are having unprotected sex. Traditional contact tracing methods may not always prove entirely reliable, but combined with this new method, we can more effectively identify which groups are most at risk, and create localised targeted public health campaigns."

There are around 17,000 cases of gonorrhoea in the UK a year, affecting mainly sub-groups of the population, with homosexual men and the Afro-Caribbean population most affected.

Professor Spratt added: "The genetic fingerprinting shows there are a number of key strains which are responsible for the bulk of infections. With this new approach we should be able to identify new outbreaks of gonorrhoea as they emerge and try to intervene and eradicate them before they become endemic."