[bastawhiz]

> If they used modern human strains too and then compared them all

Presumably the number of leprosy cases originating in modern England is near zero, so actually procuring relevant strains seems impossible, no? I can't imagine that comparing random strains from places around the would would yield interesting results.

[bennyhill]

When we are only talking about a few samples in each group, 4 cases every few years seems fine.. I would hypothesize that many of the symptomatic cases are people who are foreign but exposed to UK endemic leprosy. Of course to establish how true that is means there are more data points to collect for cases with foreign contact and the involved lands.

[bastawhiz]

I looked it up before I posted, and it's actually the opposite: the overwhelming majority of cases are from visitors to the UK who contracted the illness outside the country. The last confirmed case of leprosy being contracted in the UK was in 1953.

[pdevr]

It is very low indeed, and a large percentage of the cases are involving strains from other countries, but hopefully the number is not real zero[1], even after discounting the strains from other countries.

[1] https://bmjopen.bmj.com/content/6/5/e010608