16 February 2011, by Tom Marshall
A severe flu pandemic would send a pulse of drugs into sewage works that could endanger the UK's water treatment system, according to new research.
Sewage works rely on bacteria to break down waste so it's safe to release into rivers. If antibiotics and antiviral drugs make their way through our sewers during an influenza pandemic in the quantity predicted by recent studies, they could have a devastating effect on these bacteria.
An underperforming sewage works would release inadequately-treated sewage into a nearby river, with potentially deadly consequences for fish and other aquatic life. In many areas of southern England, drinking water itself comes from these 'at risk' rivers, so the risk of sewage work failure is immediately relevant to human health.
'The UK is one of several countries that have a robust pharmaceutical plan to tackle pandemic influenza. The massive UK antiviral stockpile will expose all UK sewage works and rivers to high concentrations of the drug during a moderate to severe influenza pandemic,' says Dr Andrew Singer at the Centre for Ecology & Hydrology, one of the authors of the report, which is published in FEMS Microbiology Letters.
'It's hard to maintain a healthy environment in a river that's one third treated sewage, even when treatment plants are working fine.'
Dr Andrew Singer, CEH
'I'd like to think there's a contingency plan for re-starting failed sewage works during an influenza pandemic – at which point there will be significant staffing challenges – but at the moment I'm not aware of one,' he continues.
In the first study of its kind, the team exposed a model sewage works to a simulated pandemic, which included an eight-week course of antibiotics and the antiviral drug Tamiflu. They then monitored the sewage works to see how well it kept functioning.
The initial few weeks of the pandemic were manageable, but as the drug onslaught continued, the 'friendly' bacteria lost much of their ability to remove nutrients and clean the water. At the peak of the pandemic the sewage works showed signs of instability and reduced treatment.
When a sewage works fails to treat waste properly, it causes serious environmental damage in the river into which it discharges the treated waste. Authorities should consider how to reduce the risk from pharmaceuticals in sewage works and rivers. This can be done by minimising the use of drugs through vaccination, and by developing contingency plans to deal with sewage works that fail during an influenza pandemic.
Safeguarding sewage plants
Treatment works have some spare capacity, but not necessarily enough. For one thing, most flu outbreaks happen in winter, when cold weather is already making them work more slowly.
Antibiotics were probably the main reason for the bacterial community's decline. These drugs do nothing to cure flu themselves, but can be needed if sufferers develop secondary bacterial infections like pneumonia or bronchitis. Singer argues that as many people as possible ought to be immunised not just against flu, but also against secondary infectious diseases like bacterial pneumonia, which account for a significant proportion of the sickness and death associated with a pandemic.
Singer says the Netherlands could provide a model for the UK. It faces similar challenges – lots of people in a small area with heavily-used rivers. 'It's hard to maintain a healthy environment in a river that's one third treated sewage, even when treatment plants are working fine,' he notes.
The Dutch water industry has coordinated plans to 're-seed' failing plants with new bacteria. This isn't a perfect solution, though; recovery can take weeks, and many Dutch engineers admit their system could be in trouble in a really serious pandemic.
If things get too serious, of course, sewage works won't be a top priority. 'If we're dealing with anything more than a mild pandemic, society is going to be concerned with saving itself; the (temporary) death of rivers will inevitably come second,' Singer observes.
'Nevertheless, we need to be conscious of the risk of multiple sewage works failing within the same river which serves as a source of drinking water,' he adds. 'This would be an inconvenience society could not afford to ignore, especially during an influenza pandemic.'
How would more vaccination help?
- The more people in a population are immune to a disease, the less likely everyone is to get it - even those who aren't immune themselves. Scientists call this 'herd immunity'.
- More flu vaccination should mean fewer people get sick and need drugs that ultimately threaten the sewage system.
- More immunisation against secondary infections (like pneumonia) will mean that even if flu does strike, fewer people need antibiotics.