In article ,
"harryagain" writes:
Total elimination is impossible.
Every puddle has it, every drain.

It's found in rain too.

But only dangerous if turned into an aerosol.

Like rain!

Anybody who thinks they can eliminate it is barking mad.
It can only be reduced & it soon breeds up again.

Some years back, a team of Italian scientists showed that
low level exposure generates immunity to it, which is not
a great surprise as that applies to many bacteria in the
environment which are potentially infectious to us, rendering
them benign as long as your immune system is working.

I suspect it will eventually be shown that the flare-ups of
legionella over the last ~40 years are actually due to our
attempts to eliminate our exposure to bacteria, including
the design of super-clean plumbing systems (which perfectly
aligns with the start of the legionella outbreaks), resulting
in many people having lost their natural immunity to something
that's probably always been in rainwater.

That doesn't mean you can ignore the problem, as regardless of
the cause, there are now a significant proportion of people
who have lost their natural immunity to it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]