No, in fact I am suggesting that H. Pylori is the cause of all peptic ulcers.

~ Barry Marshall 1983 just before an entire auditorium walked out on his presentation on the causes of peptic ulcers, previously believed to be the manifestation of a large number of distinct underlying conditions.

From Wikipedia 2012

A peptic ulcer, also known as PUD or peptic ulcer disease,[1] is the most common ulcer of an area of the gastrointestinal tract that is usually acidic and thus extremely painful. It is defined as mucosal erosions equal to or greater than 0.5 cm. As many as 70–90% of such ulcers are associated with Helicobacter pylori

Kevin Drum writes

Don’t forget lead! Lead lead lead lead. When is the connection between reduced lead levels and reduced crime levels finally going to penetrate the minds of American journalists? I know it’s not sexy and I know everyone wants to ignore it because you can’t tell heroic stories about lead, but it’s almost certainly the single biggest contributor to crime reductions nationwide.

I don’t know the research behind lead and crime. However, overwhelmingly the presumption should be that epidemics have a single precipitating factor.

People are sometimes confused by the fact that complex conditions have a long list of necessary factors. However, the odds against more than one necessary factor pushing the phenomenon across the line into epidemic at the exact same time are astronomical.

Not to go to far astray but this is why recessions likely have a single precipitating factor. They spread too fast and burn out too quickly to be multi-casual. A fifty year period of off and on stagnation, that might be multi-causal. An 18% collapse in industrial production over 18 months? That has a vector.

A good rule of thumb – I believe – for epidemics economic, biological or social is this: If it spreads along lines of communication its entropic information. If it travels along major transportation routes its microbial. If it spreads out like a fan, its an arthropod. If its everywhere, all at once, its a molecule.