Minor bugs pose epidemic threat

It seems that bacteria and viruses that have never been any threat to humans could soon be causing major epidemics. According to US and French scientists, these bugs are gaining enough of a foothold in humans to pose a serious threat.


They say that those we have eradicated through vaccines could be just one (genetic) twist away from coming back. The journal Nature says that 'epidemics are waiting to happen'.


The emergence of SARS and HIV were a complete surprise to the scientific community. The SARS virus seems to have passed from animals to humans and then from humans to humans, (scientists say).


Scientists need to find ways of predicting when pathogens (bacteria or viruses) that usually only cause a handful of cases within outbreaks are likely to turn suddenly from a minor threat to a major public health tragedy.


Scientists (Emory University, Atlanta, USA, University of Washington in Seattle, USA and Universite Pierre and Marie Curie, France, have found a way of calculating the risk from each pathogen.


These scientists have been able to calculate the 'emergence' factor by observing when a case of the illness happens (in humans), and counting how many other people caught that illness (just from that first human who caught it). If the number of people is high, then the pathogen could be dangerous.


Scientists say that a high number (of people catching the pathogen from the first case) is dangerous because if more people are carrying the pathogen there is a bigger chance of a genetic mutation taking place (of the pathogen). This increases the risk of the pathogen evolving into something better suited to attacking humans.


The researchers write, 'These long transmission chains provide an opportunity for the pathogen to adapt to human hosts, and thus for the disease to emerge.'


They say that, for example, even though we have eradicated smallpox, there is a chance that 'monkeypox' could find its way back into humans (and attack humans) as immunity to smallpox in the world population starts to decrease.


Dr. Jim Bull (University Texas) said that the days of complacency - before HIV and bio-terror - are long gone. 'It is not beyond imagination that, even with existing technology, methods could be developed for monitoring emerging pathogens.


'The means of identifying these 'epidemics-in-waiting' could become a critical tool in global defence strategy against emerging pathogens.'