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A history of legionnaires’ disease in the UK

9 Jun, 2009
Legionella pneumophila

Legionella pneumophila

Legionnaires’ disease is a rare but potentially fatal form of pneumonia. It has been a source of considerable public concern and media attention since it was first identified in 1977. John Macfarlane, Professor of Respiratory Medicine at the University of Nottingham, discusses the medical, social and legal implications of the disease.

Legionnaires’ disease got its name after an outbreak of pneumonia occurred among people attending a convention of the American Legion in July 1976 at the Bellevue-Stratford Hotel in Philadelphia, where 234 people became ill and 34 died.

“Since many of these people became ill and died after they had gone home to their different states, it took time to recognise that there was a common source,” says Professor Macfarlane. Moreover, as the causative agent did not show up on routine staining cultures, it was evident that this was a new and lethal organism. The bacterium was eventually identified in January 1977 and named Legionella, after the legionnaires attending the convention. Its source was also identified: an air-conditioning ventilator in the hotel lobby.

In 2007-08, with the help of a Wellcome Trust Research Leave Award, Professor Macfarlane spent two days a week for ten months away from his clinical duties at Nottingham University Hospitals NHS Trust, investigating the history of legionnaires’ disease in the UK. He was aided by medical historian Professor Michael Worboys at the University of Manchester.

A high-power view showing thin Gram-negative bacilli of Legionella pneumophila from a buffered charcoal-yeast extract culture.

A high-power view showing thin Gram-negative bacilli of Legionella pneumophila from a buffered charcoal-yeast extract culture.

Legionella thrives in warm, stagnant water, and people catch legionnaires’ disease by inhaling infected water droplets. “This is a unique way of catching pneumonia – usually you catch it when ordinary bacteria at the back of the throat drop down to the lung, or it develops from flu,” says Professor Macfarlane. “But you get legionnaires’ disease from infected water systems. And over the last 30 to 40 years we’ve been using a lot more artificial water systems, like showers, water-cooling towers in air-conditioning systems and other water-spray- and mist-producing equipment, which is probably why significant outbreaks started to occur during that period.”

Benidorm

The advent of cheaper flights and package tours during the 1970s made it possible for more Britons to holiday abroad. One of the most popular destinations was Spain, where new hotels were springing up. In July 1973, four tourists who stayed at the Rio Park Hotel in Benidorm contracted a mysterious form of pneumonia and died. “There was an Agatha Christie-like investigation: all the drinks and food at the hotel were tested for toxins but no one could find the cause,” says Professor Macfarlane.

Four years later, in 1977, there was another outbreak in the same hotel. Having heard of the new Legionella bacterium that had been identified, investigators sent blood samples to the USA and were able to confirm that the infection was legionnaires’ disease. They were also able to diagnose the 1973 outbreak retrospectively as the same disease.

A chest X-ray showing the shadow of legionnaires’ disease in the right lung.

A chest X-ray showing the shadow of legionnaires’ disease in the right lung.

“They found that people who showered in the morning were most at risk,” says Professor Macfarlane. “That’s because overnight, warm water is just sitting stagnant in the shower tubing – an ideal environment for Legionella to multiply in. This water is then released over the person having the first shower. Now, whenever I stay in a hotel in a warm country the first thing I do is hold my breath, turn on the shower and leave the bathroom, closing the door, to get rid of the deadleg of water in the tubing.”

A high profile

Although legionnaires’ disease is relatively uncommon (only 300-400 cases are reported in the UK each year, in contrast with many thousands of pneumonia cases), it has had a high profile from the outset, and single cases are still reported in the media.

One of the reasons for this is that legionnaires’ disease was initially hard to diagnose and treat, so it had a significant death rate and was seen as a ‘monster killer’. “At first people thought the Philadelphia outbreak was due to terrorist poisoning,” says Professor Macfarlane. “Even though the mortality rate has gone down now, people still sometimes die, or their recovery is not complete – some can still have symptoms weeks or months later and we don’t know why.”

So the disease has a degree of mystery – partly because of the unique way it is spread, and partly because it appeared to be an entirely new infection, which did not show up on routine microbiological tests, and did not respond to penicillin. “With the advent of penicillin in the 1960s to 70s, there was a feeling that pneumonia and other infectious diseases were conquered, so clinicians and researchers moved into new fields. The subsequent emergence of AIDS and other new deadly pathogens like legionnaires’ disease and Lassa and Marburg fevers was a wake-up call. It showed us that infectious diseases haven’t gone away, and reinforced the importance of microbiology and public health research.”

Medical implications

At the start of the 1980s, Professor Macfarlane helped draw up guidelines to help doctors diagnose and treat this new disease, as well as more ordinary pneumonia. At the time, tests for the disease were inadequate. “We either had to wait weeks for antibodies to show up in blood tests, or take specimens from people’s chests and culture them to test for legionnaires’ disease. That required sucking lung juice from a tube down someone’s throat, or sticking a needle in their chest. So the tests themselves could be risky and invasive, and diagnosis slow. It really came down to guesswork.”

Since the guidelines emphasised the importance of not missing legionnaires’ disease in patients presenting with pneumonia, and the disease didn’t respond to penicillin – the standard treatment for pneumonia in the 1970s – doctors were urged to prescribe additional antibiotics to cover the risk of legionnaires’ disease.

This was advantageous to the pharmaceutical industry, which put pressure on doctors to use new antibiotics. In the 1980s erythromycin was promoted as a good antibiotic for legionnaires’ disease, although it was less effective for pneumonia than penicillin.

In the 1990s a safe and rapid urine test was developed to pick up legionnaires’ disease early, dramatically changing the management of the disease in the last decade. This is one explanation for the difference in death rates in the Stafford Hospital outbreak in 1985, in which 103 cases of legionnaires’ disease were reported and 28 people died, and the outbreak in Barrow-in-Furness in Cumbria, where only seven people out of 180 who contracted the disease died. The Stafford outbreak also affected more susceptible patients with other illnesses. Chronic diseases, smoking and alcohol excess are all risk factors for infection, which is much more common in men.

Legal implications

Unlike pneumonia, which was put down to bad luck or an ‘act of God’, Legionnaires’ disease could be traced to faulty water systems, and someone, somewhere could be held accountable. The impact on legislation has been widespread.

Builders and maintenance engineers in hospitals, hotels and other public buildings have to follow increasingly stringent safety regulations. “In hospitals, the hot water has to come out of the exit at 55ºC – a temperature that will kill any Legionella in the water system – but this has the potential to scald, so hospitals have had to replace every tap with a mixer tap, at a huge cost,” says Professor Macfarlane.

Meanwhile, under civil law, people contracting legionnaires’ disease (or their families) can sue travel companies and hotels. Cases can also be brought to the criminal court. In Barrow, the source of the disease was traced to the exit of a cooling system at a council-owned arts and leisure facility in the town centre, and the senior architect at the council was tried for manslaughter for contravening health and safety legislation.

Professor Macfarlane points out the similarity with recent legislation regarding HIV. “It’s now a criminal offence to pass on the HIV virus to someone else without telling them that you’ve got it.”

 Top image credit: CDC Public Health Image Library. Other image credits: Wellcome Images.
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