Legionnaires Disease

In July 1976 the Bellevue-Stratford Hotel of Philadelphia hosted a convention of the war veterans' association American Legion.
The days following that convention were witness to a mysterious malady that afflicted 221 of the attendees, and that was ultimately the cause of the death of 34 of their number.

The illness was fairly rapidly dubbed "Legionnaires Disease", named after those first victims. Thus began the tale of this strange and insidious killer that has continued to strike people down right up to the present time.

As far as the available records show, contrary to what is commonly supposed the outbreak of 1976 was not the first of its kind. Apparently an earlier episode has been identified as having occurred in 1947 but, previous to that, the disease was completely unknown.

Because the death toll attributable to Legionnaires Disease is insignificant when measured against the likes of AIDS or cancer its failed to attract the same widespread attention as those spectres.

Probably for this very reason it largely remains something of a mystery, surrounded by far too many unanswered questions, one of which concerns the actual scale of infections, as distinct from the recorded incidents.
Disturbingly, it might be only the tip of the iceberg, unconcealable testimony to a class of activities compared to which all other forms of global pollution of the environment pale to insignificance.

Victims of the disease can exhibit flu- and pneumonia-like symptoms and, claimed not to be directly infectious, it is thought to be contracted by the inhalation of contaminated air-borne water-vapour droplets.
Thus, despite what some medical professionals claim, until the opposite can be conclusively proven person-to-person communicability should not be entirely ruled out.

A lesser-known source of infection is potting soil and garden compost.
However, the primary sources appear to be contaminated water-cooled air-conditioning systems, water evaporation units and suchlike.
So we're talking about water as the carrier, within which the Legionella bacteria thrive. Legionella is now found in virtually all natural aquatic environments but, had that always been so the probability is that the disease should have appeared and been identified long before what was actually the case.
So we must presume that water-based systems are simply the carrier, with the bacteria having been introduced at some later stage. Thus, what really needs to be addressed is the initial cause of the contamination that turns relatively innocuous water into a veritable secret killer.

Various candidates have been proposed for this contamination, from lack of maintenance right through to pigeon droppings.
Whilst the latter may be feasible given its organic component, a poorly-implemented maintenance schedule brings into being even more questions.

Are we to infer, for example, that inadequate maintenance is, in and of itself, sufficient to explain the contamination? If so, this would imply a pre-existing organism within the water that only requires "triggering".
Its not an impossible scenario of course, particularly if stagnation of the water were the actual triggering mechanism. But if that were the case, surely it wouldn't be too difficult to identify the offending organism and eliminate it before the circumstances arise that will "activate" it?

Yet this isn't the only possible scenario, nor indeed is it the most likely.
Another possibility is the introduction of an organism that only requires sufficient concentration (as might occur, for example, in an improperly maintained system) for it to become a lethal hazard.

In the absence of easily accessible data all this is of course nothing other than speculation.
Especially in the context of the bacteria's "natural habitat", given that one very likely agent of contamination has been functioning since the late 1940s it may prove particularly difficult to establish whether the bacteria has always been present in aquatic environments. Possibly the only means of making such a determination would be through the careful analysis of water samples taken from long-standing compacted ice from such as, for example, the Arctic or Antarctic.

However, this sort of speculation is imperative if we're ever to get on top of this constantly recurring problem, or even draw more attention to it. Unfortunately, its also the sort of speculation that can lead us to consider some very alarming possibilities.

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