In article ,
"john james" writes:


"Andrew Gabriel" wrote in message
...
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.

It would be interesting to see if there is any association between
those who do get severely affected by it and those who routinely
have baths rather than showers and who live where it doesn't rain
much.

A few years ago, I suggested a study to perform following an
outbreak, and got an acknowledgement from the Chief Medical
Officer's office. This was to look for a correlation. Consider
those who were exposed and infected, versus those who were
almost certainly exposed but not infected. Now check plumbing
systems they normally use (home and workplace) for no
contamination with legionella (as is likely in newer plumbing
systems) versus low level contamination with legionella (more
likely in older plumbing systems).

I would not be surprised to find those infected (particularly
if otherwise healthy) have new ultra clean plumbing systems,
and those who were not infected have older plumbing systems
with routine low level legionella contamination, affording
them immunity. There may also be a correlation with those
who work outdoors, frequently exposing themselves to rainwater,
and those who don't.

Even in full blown localised flare-ups due to high concentration
distribution of the bacteria, the proportion of people exposed
who get a noticable infection is probably tiny when you consider
city centre outbreaks still only infect a few hundred people max,
whereas it's likely 10's to 100's of thousands were exposed.

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