by Richard Knox.
Listen at
http://www.npr.org/templates/story/story.php?storyId=4473351
Syphilis epidemics may reflect immunity changes.

NPR Morning Edition
National Public Radio
February 1, 2005

Public health officials think they know what causes epidemics of
syphilis. Risky sexual behavior.

But a study in the current issue of the journal Nature suggests
that they are partly wrong.

The findings help explain why syphilis is increasing six years
after officials announced a plan to stamp out the disease.

NPRs Richard Know reports...

Fenway Community Health Center in Boston is a federally
designated sentinel site. A sort of listening post for sexually
transmitted diseases.

Infectious disease specialist Dan Cohen says some
STDs are on the rise especially syphilis...

         We definitely see a lot more ghonorrhea than we do
         syphilis. But the increase in the number of cases of
         syphilis has been more dramatic because syphilis was
         relatively uncommon in the early to mid 1990s.

In fact, in the 90s syphilis cases went down so much that in 1999
the surgeon general announced a national plan to eliminate
syphilis. That goal is now in doubt. In 2001 syphilis started to
go up again all over the country.

The latest figures show the rate is increasing 14 percent a year
among men. Ricket or syphilis epidemics are nothing new, but when
British researchers reviewed 50 years of data from 68 US cities
they found a pattern.

Syphilis epidemics peaked about every 10 years.

Nicholas Grassly of Imperial College in London says
each time there was a new explanation...

         Whether it was the sexual revolution or the gay
         liberation movement or increases in prostitution, each
         time a new social phenomenon was come with to explain
         the increases in syphilis.

But Grassly has another explanation. It has nothing to do with
behavior trends.

It reflects how the syphilis bacterium interacts with the human
immune system.

People who get syhilis become immune to it for a while.

When many people are immune there aren't as many around for the
bacterium to infect.

But over time immunity wanes and more people people age into the
sexually active years.

That provides fuel for the next epidemic.

         Certainly over the last 50 years the large increases
         and decreases in the number of cases have been driven
         by cycles in immunity not by changes in unsafe sex.

People don't become immune to ghonorrhea. And sure enough the
researchers found that ghonorrhea doesn't show the same regular
cycles as syphilis.

And they found something else interesting.

Since the 1960s syhilis epidemics in major US cities have
increasingly occurred at the same time...

         We think this reflects increases in travel and
         increases in movement. Sexual contact between peoples
         from different cities. So in other words the sort of
         sexual network across the US is becoming more
         connected.

So he says changes in sexual behavior do play a role in syphilis
epidemics.

In fact Brian Grenfell of Pennsylvania State University says it
would be wrong to think that either behavior or immunity drives
syphilis epidemics...

         In the 90s both syphilis and ghonorrhea went down
         because of behavior changes due to the AIDS
         epidemic. Both went down postwar on the advent of
         antibiotics. So their results indicate that both things
         can happen.

Greater use of condoms may explain why the current syphilis
epidemic is happening later than the usual 10 year cycle.

But that also means that there's bigger pool of susceptible
people because few are currently immune to syphilis.

Grassly says that's ominous...

         We haven't yet reached the peak. And the question will
         be how big is that peak likely to be?
         Our research suggest that it may be quite high.

It also suggests that during periods of low immunity to syphilis
like now public health agencies need to work even harder to get
people to practice safer sex.

Richard Knox NPR News Boston.
Listen at
http://www.npr.org/templates/story/story.php?storyId=4473351

Figures and tables
http://www.nature.com/nature/journal/v433/n7024/fig_tab/433366a_F1.html#figure-title
http://www.nature.com/nature/journal/v433/n7024/index.html

Grenfell page 366 News and Views
http://asi23.ent.psu.edu/onb1/publ/grassly/grenfellbjornstad.pdf
PDF online viewer at
http://view.samurajdata.se

http://tinyurl.com/bokbj
http://66.102.7.104/search?q=cache:jh5snzj75oUJ:asi23.ent.psu.edu/onb1/publ/gras
sly/grenfellbjornstad.pdf

Grassly page 417 Letters to Nature
http://www1.imperial.ac.uk/_Resources/(C73E365C-DD68-41B3-BFA1-C4CF03AC19CA)/nat
ure03072.pdf
PDF online viewer at
http://view.samurajdata.se

http://tinyurl.com/cl893
http://66.102.7.104/search?q=cache:aOH1q6r4gkgJ:www1.imperial.ac.uk/_Resources/(
C73E365C-DD68-41B3-BFA1-C4CF03AC19CA)/nature03072.pdf

On the cover,
the syphilis pathogen Treponema pallidum
in a coloured transmission electron micrograph, x16,000 approx.
Alfred Pasieka / Science Photo Library
http://www.nature.com/nature/journal/v433/n7024/edsumm/e050127-01.html
http://www.nature.com/nature/journal/v433/n7024/index.html