Under the Weather Climate, Ecosystems, and Infectious Disease (2001) / Chapter Skim
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Climate Influences on Specific Diseases
Climate Influences on Specific Diseases
Pages 45-58
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From page 45... ...
In terms of the number of human infections occurring globally, dengue is considered to be the most important arthropod-borne viral disease in humans. The symptoms of dengue include fever, severe headache, muscle and bone pain, and occasionally shock and fatal hemorrhage.
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From page 46... ...
UNDER THE WEATHER Cq so o O o ·_4 3 an ·_4 C)
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From page 47... ...
Heavy rainfall tends to overflow containers and can thus discourage vector breeding, while extended drought conditions have in some cases led to higher vector abundance due to an increased use of water storage containers. Saturation deficit, a parameter taking into account both temperature and relative humidity, affects the survival of eggs and adults.
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From page 48... ...
The pathogens are protozoan parasites in the genus Plasmodium that are transmitted to humans by the Anopheles mosquito. In humans the malarial parasites infect red blood cells, causing periodic chills and fever, and in some species of Plasmodium the parasites can ultimately cause death.
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From page 49... ...
Mild infections cause fever and headache, but more severe infections may cause encephalitis, with symptoms of headache, high fever, neck stiffness, stupor, disorientation, coma, and paralysis. The disease occurs in North America, and the virus is closely related to the Japanese encephalitis virus of Asia and West Nile virus of Africa, Eurasia, Australia, and North America.
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From page 50... ...
The virus also has a rural cycle in the western United States, where the Culex tarsalis mosquito is the major vector. This mosquito breeds in flood waters and is abundant in irrigated fields and riverine flood plains, and thus excess rainfall and abundant snowmelt can favor its breeding (Monath, 1980~.
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From page 51... ...
Such outbreaks induce protective immunity in all infected animals, thus reducing the number of susceptible animals after an epizootic. Human proximity to infected animals and mosquitos partly determines disease risk to people.
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From page 52... ...
Data from an ongoing study of Peromyscus rodents revealed that in 1993 populations of this animal in some parts of New Mexico were as much as 10 times greater than average (Parmenter et al., 1993~. The hypothesis was advanced that the unusually heavy rainfalls occurring during the 1992-1993 E1 Nino led to an abundant food supply for rodents, followed by a rodent population explosion.
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From page 53... ...
Climate change scenarios often forecast that some regions of the United States may become warmer and moister, leading to speculation that the range of deer ticks carrying Lyme disease might expand. However, the current distribution of the deer tick and of Lyme disease in the Unites States spans a wide range of climatic conditions, and deer ticks are already abundant in parts of the country where cold extremes are common.
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From page 54... ...
The range of factors that presently limit distribution of the vector remain poorly understood, but research suggests that microclimate, abundant hosts, and suitable vegetation and soil habitat are important. The tick has not yet become established or widespread in apparently appropriate environments in many areas of the United States, thus indicating that even where suitable microclimate, host, pathogen, and human contact conditions appear to exist, Lyme disease may not be present.
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From page 55... ...
The interannual variability in the virulence of influenza strains makes interpretation of the relevant data difficult. One common explanation for influenza's seasonal cycle is that there is more indoor crowding in the winter, which leads to greater disease transmission.
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From page 56... ...
This suggests that land use in key watersheds is an important factor, facilitating transport of fecal contaminants from both human sewage and animal wastes into waterways and drinking water supplies during heavy precipitation. The occurrence of Cryptosporidium in surface waters has been reported in 4 to 100 percent of samples examined (Lisle and Rose, 1995~.
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From page 57... ...
Cholera is a diarrhea! disease caused by the human pathogenic bacterium, Vibrio cholera.
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From page 58... ...
The confirmation that V cholerae occurs in aquatic environments in association with zooplankton and phytoplankton, and the associations found between cholera cases and sea surface temperature and sea surface height, combine to provide evidence that some cholera epidemics are indeed influenced by climate.
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