I was on a small mammals training course and the professor was warning of the dangers of Leptospirosis. Apparently 5-40% of Rats have it and an unknown proportion of other animals. The warning sheet they handed out listed farmers, gardeners, etc as 'at risk' groups. I looked it up on the NHS website out of interest but it said there were only about 25 cases a year in the UK, even of the mild form.
I understand that it dies when it's dried out, but still, in notoriously rainy Britain, I can't seem to make sense of the numbers. There are at least half a million farmers in our country, probably a similar amount of gardeners, at least several thousand homeless and poverty stricken who must live in very close proximity to the huge urban Rat population, not to mention the potential for rodents to get into domestic water tanks. In rainy weather everything can stay wet for days. Also, if I remember rightly, an Olympic athlete recently died from it, so it obviously doesn't require a weak physiology to get in.
So, the question is, given what seems to me to be a massive prevalence (40% of all Rats), vast contact opportunities (all land workers during spells of wet weather), and seemingly a tough little organism (can kill an Olympic athlete), why is it so rare (25 cases in 70,000,000 people)?