By Vivienne Parry
Presenter, Radio 4's Disease Detectives |
 And, in an increasingly globalised world, there is no certainty about when or where they will strike - whether it is Sars or bird flu - bio-terrorism or natural disaster.  Experts around the world track down the sources of new diseases |
But an international health force is on permanent duty, constantly on the alert for new and emerging disease. At its core are the disease detectives - an extraordinary band of men and women around the world, dedicated to tracking down infectious disease - before it finds us. In the years following WWII, it was thought that humans were winning the centuries old conflict with infectious disease. The newly discovered antibiotics had conquered TB and typhoid, vaccination had vanquished polio, diphtheria and whooping cough. Better sanitation had banished the spectre of cholera. But the celebrations were premature. Even by the 1950s, bacteria were becoming resistant to penicillin. And a deadly crop of new diseases has appeared; amongst them, SARS, West Nile virus, Ebola and of course HIV. The complacency of the post war years vanished to be replaced by the growing concerns about the threats infectious disease pose, not just to individual countries, but in the days of rapid air travel and mass human migration, to the entire world. The disease detective's job is to find, identify and contain that threat, using sleuthing methods familiar to every criminal detective. "Most outbreaks work the same way," says Dr Ali Khan, epidemiologist at the Centers for Disease Control (CDC) in Atlanta, US. "You don't get to see the whole picture, you get a slice and the slice you see is a lot of people sick. "If you think about detectives that's all they get too: a crime scene and from that they need to put the pieces together and say 'Who did it?''. We do 'Who did it?' every day". Deadly water Sherlock Holmes has nothing on the disease detectives. Take for instance the strange case of cholera and the Broadwick Street water pump, investigated by Victorian physician, Dr John Snow, one of the first disease detectives. In August 1854 only a few cholera deaths had been reported in London's Soho district. But on the night of 31st August, 56 cases were reported. The next day it was 143. By September 1st, 70 people had died. Snow was determined to find the source of the outbreak. Armed with lists of the affected homes, he deduced that most of the deaths were close to a single water pump in Broadwick Street. But what finally confirmed the pump as the source were two seemingly unrelated cases, miles away from Soho. When Snow investigated the death of a woman in Hampstead, he discovered that she'd so liked the taste of the Broadwick Street pump water that she'd had it delivered to her twice a week. On 31st August, she and her niece drank from the new delivery. Her niece then returned to her home to Islington. Both died of cholera two days later. Case solved. Car park The proverbial needle in the haystack would be easier to find than the causes of some disease outbreaks. Just as in a criminal investigation, huge amounts of data are collected by highly trained methodical investigators, which then have to be sifted in a search for the patterns which will lead them to the culprit. One case from Britain's highly respected Health Protection Agency illustrates the problems. At the end of July 2002 the HPA received reports of three unusual cases of pneumonia, all from hospitals in the North of England. The agency's microbiologists confirmed they were caused by Legionella, the bug that causes Legionnaire's Disease. But were these cases linked or was this coincidence? Two of the cases had an obvious connection - Barrow-in-Furness. As two further cases were notified from the town, the outbreak control team assembled. Within a day, 20 more cases had been identified. The team pored over hundreds of questionnaires, trying to find a common link which they eventually discovered was ¿ taking the short cut from a car park to a hardware shop. Legionnaire's Disease, named after the very first outbreak at a convention for the American Legion in Philadelphia, is spread in water droplets and is associated with showers, swimming pools and water cooling plants. A carefully plotted map of air conditioning units in the area showed that one from a council owned building discharged into an alleyway - which happened to be a shortcut from a car park to a hardware shop. When the air conditioning unit was tested, it contained Legionella. Case solved. 'Unsung heroes' And just like TV programme 'Waking the Dead', the disease detectives work with cold cases. DNA fingerprinting has revolutionised the quest for suspects and Jeff Taubenberger of the US Armed Forces Institute of Pathology in Washington DC has been using it to try and unlock the secrets of the 1918 Spanish Flu virus, which killed over 40m people. These secrets may well have relevance in defending ourselves from an avian flu pandemic today. "The Spanish Flu is one of the great medical mysteries of all time" says Taubenberger. "We thought all along that finding out what happened in 1918 would very likely be relevant to understanding how it is that flu virus can cause pandemics, and why they can be so virulent. "Our detective work with the 1918 pandemic suggests very strongly it was a bird-like virus". Much of this work is potentially highly dangerous. For instance, disease detectives from the CDC, the American counterpart to Britain's HPA, investigated an outbreak of disease in the Congo in 1976 knowing that over 90% of people infected, died horribly within a few days. Here the source of the outbreak was found to be bats. Today we know the disease to be the deadly Ebola haemorrhagic fever. The disease detectives are unstinting in their dedication to public health and it is their detailed methodical science that keeps us all safe. We should be very grateful to this courageous band of unsung heroes. Hear episode 1 of Disease Detectives at Radio 4's page.
Episode 2 is at 1100 GMT on Wednesday, 15 February, 2006 on Radio 4. Listen again | 
We do 'Who did it?' every day 
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