After this outbreak
in Edinburgh, don't
knock health and safety
The current outbreak of legionnaires' disease in Edinburgh has understandably attracted much attention in the press. As someone who was a chest physician when it was first discovered and who has both treated patients with it and advised companies on its prevention, I can see both sides of the story. It is both an old one and a new one.
The old story is biology. Both humans and microbes are simply organisms adapted more or less to our ecological niche on the planet. At times we compete, at others we collaborate. We use bacteria, in our guts for example, where we call them commensals, literally dining at the same table, and in the production of bread and wine, as other examples. At other times we compete, when they may cause disease such as pneumonia.
During my early childhood there were few if any antibacterial treatments available and we took our chances with infections, but since then man's ingenuity has resulted in the development of many new antibiotics. Some doctors thought that we had the upper hand, but this was a vanity; bacteria mutate many times daily and resistant organisms quickly develop unless we use our treatments wisely. Doctors and public health officials have to collaborate closely to prevent the rise of dangerous resistant organisms and doctors who do not subscribe to this become public health risks themselves.
The new story is this. In 1976 we doctors were in a fairly complacent phase as bacterial resistance was not yet a great problem, and then came an outbreak of over 100 cases of severe pneumonia among delegates to a conference of the American Legion in Philadelphia. Standard bacterial tests failed to find the organism and it did not respond to the usually effective antibiotics, but fortunately, in a search for rarer causes of pneumonia, some material from the lungs of deceased victims was inoculated first into guinea pigs then into chick embryo yolk sacs, and a previously unknown bacteria was found and named Legionella.
Research rapidly found better ways of identifying it and it was found to prefer to reproduce inside the body's defensive cells, so that the antibiotics usually given for pneumonia like the penicillins were ineffective. Other antibiotics that penetrated cells better, such as erythromycin, tetracycline and rifampicin proved effective and were available in the mid 1970s, so it became curable.
The particular niche that legionella organisms inhabit is water, and we usually catch them by inhaling droplets when water is aerosolised. They particularly like to live in a biological soup-like environment as they multiply in cells of other organisms and they prefer warmth; thus sludge of biological matter building up on the slats of cooling towers for air conditioning or in the bottoms of tanks for recirculating hot water systems are favoured environments.
The good news for Edinburgh is that the doctors were on the ball and the public health authorities very quickly took appropriate action by finding
the likely sources and acting to decontaminate them.
If sufficient numbers of legionella build up and are released in vapour from the system, as may happen in factories, hospitals and hotel showers for example, people in that vicinity are at risk. Thus, outbreaks such as the Edinburgh one may occur, but also sporadic cases happen quite frequently as a result of the misfortune implicit in life when a vulnerable person encounters droplets containing the organisms.
The two sides of legionnaires' disease are prevention and cure. Prevention is dealt with by informing the owners of buildings and factories of the need to take certain precautions if they have circulating hot water systems that can release vapour, an important role of the oft derided Health and Safety Executive. The media reports have emphasised disinfection but this, using chlorine releasing agents, is only a part of the management and though essential may be dangerous by causing complacency, since if sludge builds up the disinfectant has difficulty penetrating it. It is therefore critically important to prevent this build up of sludge by cleaning of cooling towers. It may also be necessary to raise the temperature of the system to a level at which the organism's growth is inhibited.
Cure depends on doctors being aware of the possibility of this cause of pneumonia and making the diagnosis early, not as easy as you might think. Happily, most chest specialists are well aware of the possibility and facilities for quick diagnosis and for treating the most severely affected are widely available, as they were in the Edinburgh outbreak.
As with all infective diseases, the organism does not cause disease in everyone who is exposed to it; personal resistance differs greatly and (inevitably, I'm afraid) smokers and people with other lung disease are particularly vulnerable. In such people particularly the illness may be severe, complicated by other manifestations, and sometimes fatal. Fit young people may well get a good dose of bacteria and develop no more than an antibody response in their blood. If treated with appropriate antibiotics, the large majority recover from the acute illness quickly, though it often leaves them feeling ill for weeks afterwards.
The good news for Edinburgh is that the doctors were on the ball and the public health authorities very quickly took appropriate action by finding the likely sources and acting to decontaminate them. But the sad news of death and serious illness is a reminder that we are but part of the great ecology of the planet and have to coexist with its other inhabitants, making sure we are as well adapted to our environment as possible and pay due respect to bacteria. Next time you read of complaints about 'health 'n safety' and reducing red tape in industry, remember that there is a reason for this.
Professor Anthony Seaton is an emeritus professor in the school of medicine and dentistry at the University of Aberdeen