Johns Hopkins Gazette: January 22, 1996

The heat is on
Disease Will Spread As Globe Warms

     So often, the timing of truths is stranger than fiction. 

     In the midst of one of Maryland's snowiest Januarys and on
the heels of one of the state's worst blizzards of this century,
comes a study from the School of Public Health reporting that the
Earth is actually getting warmer. And at a potentially alarming

     In findings published in the Jan. 17 issue of the Journal of
the American Medical Association, lead author Jonathan Patz
reported that the average global temperature is expected to rise
2 degrees Celsius (35.6 degrees Fahrenheit) during the next 100
years. The slight increase, the report said, could contribute to
a worldwide surge in infectious diseases, especially those
transmitted by insects and water. 

     The report also notes that a simultaneous rise in ocean
waters by 6 inches to 3 feet also may increase the prevalence of
infectious diseases.

     Since the late 1890s, the average global temperature has
risen .5 degrees Celsius. The predicted increase is a fivefold
faster rate of increase, which Patz, a research associate in the
Department of Molecular Biology and Immunology, said results from
an increase in carbon dioxide.

     Climate changes are likely to have the greatest effect on
the spread of malaria and dengue, the report notes. 

     Currently, about 2 billion people worldwide are at risk for
contracting the mosquito-borne malaria. Patz said the rise in
temperature would put an additional 620 million people at risk by
the year 2050, which he added would cause 1 million additional
malaria-related deaths annually. 

     Dengue is another infectious tropical disease transmitted by
mosquitos. It is characterized by severe pain in the joints and
back, accompanied by fever and skin rashes. The major mosquito
carrier of dengue cannot survive freezing temperatures, and the
malaria parasite cannot develop at temperatures below 16 degrees
Celsius, or 60.8 degrees Fahrenheit. 

     Global warming, the report says, would increase the
mosquitos' geographic range, allowing them to carry diseases to
places previously protected by colder temperatures. 

     At a news conference last week, Patz and his colleagues from
Harvard University and George Washington University said,
"Climate is not the only factor driving these diseases." They
said that at-risk populations could reduce their chances of
exposure by taking measures such as putting screens on windows
and limiting the amount of standing water in populated areas.

     The report notes that other diseases that may increase with
global warming include river bindness, prevalent in West Africa;
sleeping sickness, commonly diagnosed in sub-Saharan Africa; and
St. Louis encephalitis, indigenous to the United States among
other locales.

     "These long-term ecological and climatological changes
portend serious and widespread public health threats," Patz said. 

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