Diseases are a little like stock market fluctuations and economic booms and busts: they are cyclical. Doctors like to tell us that their ministrations eradicate disease, but in truth they're merely taking the credit for a downshift in the cycle.
It's happened recently with TB, and now doctors are reporting an alarming increase in cases of syphilis.
Doctors were confident that they had defeated the sexually-transmitted disease by the 1980s. Cases were low, and remained so, throughout the decade, but between 1997 and 2003 there has been a colossal increase, in some quarters as high as 1400 per cent.
The 'at risk' groups include homosexuals, prostitutes and drug users who inject - as its always been.
The one difference, doctors assume, is that people in the gay community are taking a more relaxed view about protective sex following the AIDS scare, which also happened to start in the 1980s.
The problem with cyclical diseases is that a whole new generation of doctors has arrived, and one which can't easily identify symptoms of a health problem that had almost gone away. Worse, they may even be unsure about how to treat it.
(Source: The Lancet, 2007; 369: 1912-4).