US syphilis epidemics not driven by increases in unsafe sex say researchers

January 26, 2005

A UK based team of researchers has found that regular epidemics of syphilis in the USA are due to the intrinsic cyclical nature of the disease. They show that changes in the immunity of the population cause periodic syphilis outbreaks, rather than changes in sexual behaviour, as was previously thought.

According to research published today in Nature, the team from Imperial College London and funded by the Medical Research Council and the Royal Society suggest that syphilis outbreaks, previously attributed to social phenomena such as the sexual revolution or the gay liberation movement, are actually caused by a loss of immunity among those at risk of infection.

Dr Nicholas Grassly, from Imperial College London, based at St Mary's Hospital and one of the researchers said: "While we do not dispute the fact that syphilis is transmitted by unsafe sex, our findings suggest that change in population immunity is the main reason for periodic epidemics of syphilis, not change in sexual behaviour."

After analysing data from 68 cities across the USA since the 1940s, the team found that rises and falls in the disease followed a distinct pattern that was repeated over a 10-year cycle. Rises in syphilis cases can be explained by falling population immunity. Immediately after an epidemic, immunity is at its highest. It then takes time for immunity to drop to a level when an epidemic can occur again.

The team compared syphilis case reports with gonorrhoea reports from the same cities and found contrasting results. Despite infecting the same groups, cyclical epidemics of gonorrhoea did not occur because there is no immunity to re-infection with this disease. Change in the numbers of new gonorrhoea cases is therefore more likely to reflect change in sexual behaviour rather than the cyclical natural phenomenon seen with syphilis.

Dr Grassly, a Royal Society University Research Fellow, adds: "It is striking how the repeated epidemics of syphilis are predicted by what we know about the natural history of infection. As well as analysing previous epidemics it may also be possible to use these findings to help doctors and sexual health workers predict and prepare for future outbreaks of the disease. Troughs in the number of cases offer an unprecedented opportunity for eradication of the disease. However, when this opportunity is missed, an epidemic is likely to follow."

The researchers believe the role of population immunity highlights the need to carefully interpret data from routine surveillance studies, where changes in the rate of new infections may not always be attributable to changes in behaviour or the environment.
-end-


Imperial College London

Related Syphilis Articles from Brightsurf:

New research reveals risky sexual behavior and STIs are rising despite COVID-19 pandemic
New research launched at the 29th EADV Congress, EADV Virtual, has found that despite the COVID-19 (SARS-CoV-2) lockdown restrictions, diagnosis of sexually transmitted infections (STIs), including gonorrhoea, secondary syphilis and mycoplasma genitalium (MG), have increased.

Syphilis may have spread through Europe before Columbus
Columbus brought syphilis to Europe -- or did he? A recent study conducted at the University of Zurich now indicates that Europeans could already have been infected with this sexually transmitted disease before the 15th century.

One in five Georgian Londoners had syphilis by their mid-30s
250 years ago, over one-fifth of Londoners had contracted syphilis by their 35th birthday, historians have calculated.

Tropical disease in medieval Europe revises the history of a pathogen related to syphilis
Plague was commonplace in medieval times, so finding its victims in a 15th century Lithuanian graveyard was no surprise.

Syphilis eludes immune attack by altering a single gene
Shuffling of DNA in a single gene might be why the syphilis bacteria can evade the immune system.

Health care in baboons
Sexually transmitted diseases reduce the willingness of female baboons to mate.

Syphilis infection rates in dialysis patients exceed general population
Syphilis rates, like other sexually transmitted disease rates in the United States, are soaring, and the first known study to examine syphilis rates in patients with kidney failure found an incidence greater than three times that of the general population.

NIAID officials call for innovative research on sexually transmitted infections
Sexually transmitted infections, or STIs, pose a significant public health challenge.

Europe: syphilis notifications up by 70% since 2010
The number of syphilis cases has been consistently going up across Europe since 2010, mostly affecting men who have sex with men living in urban areas.

USPSTF recommendation statement on screening for syphilis infection in pregnant women
The US Preventive Services Task Force (USPSTF) recommends early screening for syphilis infection in all pregnant women.

Read More: Syphilis News and Syphilis Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.