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Beyond the fire-hazard mentality of medicine: the ecology of infectious diseases.

Bradbury J - PLoS Biol. (2003)

View Article: PubMed Central - PubMed

Affiliation: janeb@sciscribe.u-net.com <janeb@sciscribe.u-net.com>

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At the same time, old enemies such as dengue and hantavirus pulmonary syndrome have re-emerged to cause important human epidemics... By 1995 that figure had more than quadrupled... Greater urbanisation, human population growth, increased human travel, and a global reduction of effective mosquito control programmes have all been implicated in the observed changes in dengue dynamics... Then, in 1999, the first 62 cases were reported in the United States... Last year, there were 4,156 human cases in the United States and West Nile virus was found in all but six states... Duane Gubler, director of the Division of Vector-Borne Diseases at the United States' Centers for Disease Control and Prevention (CDC; Fort Collins, Colorado, United States), is under no illusion that preventing West Nile virus disease outbreaks will be easy. ‘We really don't know enough about the ecology of this disease to target our control efforts appropriately’, he says. ‘We know that the mosquito–bird–viral maintenance cycle requires certain species of birds, but we don't know all the bird hosts’... Malcolm is trying to predict whether West Nile virus disease could establish itself in the United Kingdom. ‘There must be a big difference between the ecology and biology of the different physiological forms of Culex pipiens in Europe, where it only causes sporadic West Nile outbreaks, and the United States where it has spread like wildfire’, says Malcolm. ‘We need to understand that difference and to know exactly which Culex pipiens we have in the UK’... The British Culex pipiens pipiens mosquito is mainly a bird biter, he explains, while the British Culex pipiens molestus is a mammal feeder. ‘But we don't know the extent to which our bird-biting mosquito bites people or whether the human-biting form ever bites birds’, and for the virus to be transmitted from birds to people, not only does the virus have to be in birds, but there has to be a vector that will bite both... However, even if the indigenous mosquito populations in the United Kingdom do not bridge the gap between birds and people, ‘the characteristics of our native mosquitoes could change’, warns Malcolm, possibly through mating with an imported mosquito... In the case of hantavirus, says James Mills, chief of the CDC Medical Ecology Unit (Atlanta, Georgia, United States), ‘as human influences reduce the diversity of rodent assemblages, the prevalence of hantavirus infection in the favoured host species increases’... For other rodent-borne diseases, an awareness of when rodent populations are increasing is already passed onto the general public, and for those rodents that enter human habitation, this can be accompanied by advice on how to avoid rodent infestations in homes... Similarly, for mosquito-borne diseases, education about how to avoid mosquito bites can go some way to reducing the magnitude of disease outbreaks... The researchers have been able to correlate changes in rodent populations with wide-scale vegetation changes detected through satellite monitoring and, as a result, says Yates, ‘we can now predict about 88% of the time what the risk of hantavirus infection is at any given place about six months in advance’... In the first 60 years of the 20th century, comments Gubler, many arboviral diseases were well controlled, but as attention turned to high-tech solutions such as vaccines, little money was provided for continued research in disease ecology and prevention research... A return to a fully integrated approach to control and prevention is essential, concludes Gubler, if emerging infectious diseases are going to be adequately controlled, particularly in tropical countries where they continue to be a pressing problem.

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The Host for HantavirusThe deer mouse (P. maniculatus) is the reservoir host for the Sin Nombre hantavirus, the cause of hantavirus pulmonary syndrome. (Picture courtesy of the CDC and the Partnership, Inc.)
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pbio.0000022-g004: The Host for HantavirusThe deer mouse (P. maniculatus) is the reservoir host for the Sin Nombre hantavirus, the cause of hantavirus pulmonary syndrome. (Picture courtesy of the CDC and the Partnership, Inc.)

Mentions: In every case, the more warning that can be given of an impending outbreak and the more details of its location and timing, the more that can be done to reduce the human disease burden. Work being done by Mills, Yates, and their colleagues provides a good illustration of how, at least for the Sin Nombre hantavirus, greater predictive accuracy is becoming a reality. Hantavirus pulmonary syndrome outbreaks, which are caused by the Sin Nombre virus, occur when deer mouse (Peromyscus maniculatus) (Figure 4) populations and other infected rodent numbers increase. Monitoring these changes on the ground can only give local information and cannot provide much notice of increased human hantavirus risk. However, as Mills explains, long-term ecological studies have shown that deer mice populations increase a year after El Niño climatic events as a result of an increased food supply. The researchers have been able to correlate changes in rodent populations with wide-scale vegetation changes detected through satellite monitoring and, as a result, says Yates, ‘we can now predict about 88% of the time what the risk of hantavirus infection is at any given place about six months in advance’. More recently, the researchers have developed their models further to predict the existence of refugia, ecologically distinct areas where the virus survives hidden within focal mouse populations between human outbreaks. Finally, in a collaboration with physicists, theoretical predictive models based on wave theory have been built that, if they can be empirically verified, will provide an even earlier prediction of when and where hantavirus outbreaks will occur by predicting viral spread from the refugia, says Yates.


Beyond the fire-hazard mentality of medicine: the ecology of infectious diseases.

Bradbury J - PLoS Biol. (2003)

The Host for HantavirusThe deer mouse (P. maniculatus) is the reservoir host for the Sin Nombre hantavirus, the cause of hantavirus pulmonary syndrome. (Picture courtesy of the CDC and the Partnership, Inc.)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC261872&req=5

pbio.0000022-g004: The Host for HantavirusThe deer mouse (P. maniculatus) is the reservoir host for the Sin Nombre hantavirus, the cause of hantavirus pulmonary syndrome. (Picture courtesy of the CDC and the Partnership, Inc.)
Mentions: In every case, the more warning that can be given of an impending outbreak and the more details of its location and timing, the more that can be done to reduce the human disease burden. Work being done by Mills, Yates, and their colleagues provides a good illustration of how, at least for the Sin Nombre hantavirus, greater predictive accuracy is becoming a reality. Hantavirus pulmonary syndrome outbreaks, which are caused by the Sin Nombre virus, occur when deer mouse (Peromyscus maniculatus) (Figure 4) populations and other infected rodent numbers increase. Monitoring these changes on the ground can only give local information and cannot provide much notice of increased human hantavirus risk. However, as Mills explains, long-term ecological studies have shown that deer mice populations increase a year after El Niño climatic events as a result of an increased food supply. The researchers have been able to correlate changes in rodent populations with wide-scale vegetation changes detected through satellite monitoring and, as a result, says Yates, ‘we can now predict about 88% of the time what the risk of hantavirus infection is at any given place about six months in advance’. More recently, the researchers have developed their models further to predict the existence of refugia, ecologically distinct areas where the virus survives hidden within focal mouse populations between human outbreaks. Finally, in a collaboration with physicists, theoretical predictive models based on wave theory have been built that, if they can be empirically verified, will provide an even earlier prediction of when and where hantavirus outbreaks will occur by predicting viral spread from the refugia, says Yates.

View Article: PubMed Central - PubMed

Affiliation: janeb@sciscribe.u-net.com <janeb@sciscribe.u-net.com>

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

At the same time, old enemies such as dengue and hantavirus pulmonary syndrome have re-emerged to cause important human epidemics... By 1995 that figure had more than quadrupled... Greater urbanisation, human population growth, increased human travel, and a global reduction of effective mosquito control programmes have all been implicated in the observed changes in dengue dynamics... Then, in 1999, the first 62 cases were reported in the United States... Last year, there were 4,156 human cases in the United States and West Nile virus was found in all but six states... Duane Gubler, director of the Division of Vector-Borne Diseases at the United States' Centers for Disease Control and Prevention (CDC; Fort Collins, Colorado, United States), is under no illusion that preventing West Nile virus disease outbreaks will be easy. ‘We really don't know enough about the ecology of this disease to target our control efforts appropriately’, he says. ‘We know that the mosquito–bird–viral maintenance cycle requires certain species of birds, but we don't know all the bird hosts’... Malcolm is trying to predict whether West Nile virus disease could establish itself in the United Kingdom. ‘There must be a big difference between the ecology and biology of the different physiological forms of Culex pipiens in Europe, where it only causes sporadic West Nile outbreaks, and the United States where it has spread like wildfire’, says Malcolm. ‘We need to understand that difference and to know exactly which Culex pipiens we have in the UK’... The British Culex pipiens pipiens mosquito is mainly a bird biter, he explains, while the British Culex pipiens molestus is a mammal feeder. ‘But we don't know the extent to which our bird-biting mosquito bites people or whether the human-biting form ever bites birds’, and for the virus to be transmitted from birds to people, not only does the virus have to be in birds, but there has to be a vector that will bite both... However, even if the indigenous mosquito populations in the United Kingdom do not bridge the gap between birds and people, ‘the characteristics of our native mosquitoes could change’, warns Malcolm, possibly through mating with an imported mosquito... In the case of hantavirus, says James Mills, chief of the CDC Medical Ecology Unit (Atlanta, Georgia, United States), ‘as human influences reduce the diversity of rodent assemblages, the prevalence of hantavirus infection in the favoured host species increases’... For other rodent-borne diseases, an awareness of when rodent populations are increasing is already passed onto the general public, and for those rodents that enter human habitation, this can be accompanied by advice on how to avoid rodent infestations in homes... Similarly, for mosquito-borne diseases, education about how to avoid mosquito bites can go some way to reducing the magnitude of disease outbreaks... The researchers have been able to correlate changes in rodent populations with wide-scale vegetation changes detected through satellite monitoring and, as a result, says Yates, ‘we can now predict about 88% of the time what the risk of hantavirus infection is at any given place about six months in advance’... In the first 60 years of the 20th century, comments Gubler, many arboviral diseases were well controlled, but as attention turned to high-tech solutions such as vaccines, little money was provided for continued research in disease ecology and prevention research... A return to a fully integrated approach to control and prevention is essential, concludes Gubler, if emerging infectious diseases are going to be adequately controlled, particularly in tropical countries where they continue to be a pressing problem.

Show MeSH
Related in: MedlinePlus