Lessons from the past: Evolution of Syphilis in Renaissance Europe sheds light on spread of diseases today

10 December 2003

The new theory, by Dr Robert Knell at Queen Mary’s School of Biological Sciences, suggests that when syphilis first appeared it was too virulent for its own good. Many of the early symptoms of the epidemic – such as disfiguring pustules on the face accompanied by a foul smell – would have been obvious to any potential sexual partners of a sufferer, enabling people to avoid the infected person and thereby reducing transmission. Other symptoms, such as agonising pains in the joints, would have effectively disabled the sufferer, or at least distracted them from seeking out new sexual partners. As a result, less virulent strains of the disease were transmitted more often, thus leading to changes in the severity of the disease.

Changes in virulence in diseases introduced to animal populations have been observed before, but this is believed to be the first credible example of such rapid changes occurring in a human disease. This is an important step forward in understanding how dangerous new diseases such as SARS or Ebola virus might change if they become endemic in the human population. In addition, the possibility of syphilis evolving to become less noticeable is of concern because it can enhance the transmission of HIV.

Dr Knell says: "Syphilis changed from a virulent disease to a relatively mild one in a very short period. Our use of antibiotics to treat it means that it may still be evolving towards lower virulence. Syphilis is rare nowadays but its incidence is rapidly increasing, and in recent outbreaks in the UK some of those infected noticed no symptoms at all. This could have serious implications concerning the spread of infectious diseases such as HIV because the chance of contracting HIV through heterosexual sex with someone who is HIV positive is about thirty times greater if you have syphilis."

Syphilis first appeared in Europe in 1496 and was known as the ‘Great Pox’ or ‘French Disease’. At first it caused terrible sickness, including severe ulceration of the part of the body first infected (often the genitals), pustules, soft tissue being eaten away to the bone, and the rapid onset of ‘gummy’ tumours. However, within fifty years syphilis changed from an acute, severe and debilitating disease to the milder infection that is modern syphilis.

Dr Knell writes in the Royal Society journal Biology Letters that the decline in the virulence of syphilis was noted as early as five to seven years from the start of the epidemic – less than a single generation and too short a time for any resistance to the disease to be formed. This would indicate that, rather than there being any changes in people’s immune systems, it was in fact the disease that evolved during this period.

Notes to Editors:

Queen Mary, University of London

• Queen Mary is one of the leading colleges in the federal University of London, with over 11,000 undergraduate and postgraduate students, and an academic and support staff of around 2,600.

• Queen Mary is a research university, with over 80 per cent of research staff working in departments where research is of international or national excellence (RAE 2001).  It has a strong international reputation, with around 20 per cent of students coming from over 100 countries.

• The College has 21 academic departments and institutes organised into three sectors: Science and Engineering; Humanities, Social Sciences and Laws; and the School of Medicine and Dentistry.

• It has an annual turnover of £200 million, research income worth £43 million, and it generates employment and output worth nearly £400 million to the UK economy each year.

• Queen Mary’s roots lie in four historic colleges: Queen Mary College, Westfield College, St Bartholomew’s Hospital Medical College and the London Hospital Medical College.

• The School of Biological Sciences
  The School of Biological Sciences is a dynamic department with 37 academic staff and over 500 undergraduate and postgraduate students.
  Researchers carry out nationally and internationally renowned research, studying basic mechanisms and processes of life from the molecule to the ecosystem. Staff research interests fall into four broad areas; Aquatic and whole organism biology; Evolutionary genetics; Neuronal and hormonal signalling; and Protein structure and function.
  The School recently launched the Centre for Life Sciences to facilitate research at the level of the molecule, the cell and the whole organism. The Centre is funded by a grant from the Science Research Infrastructure Fund and equipped with state-of-the-art analytical equipment.

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