Global Warming and
Infectious Diseases
Joseph witzke
Climatology
November 2010
So What?
Diseases Kill people and animals
There may be a correlation between global warming and spread
of infectious diseases
So if you believe that the earth is going to continue to warm at
an alarming rate you better get your vaccinations because the
diseases may get you before the heat does!
But warming may not be the only factor...
Some Questions
Will a rise in global temperatures increase the intensity and
frequency of infectious diseases?
Does the geographic range of these diseases simply increase?
Or will there just be a shift in the Regions of these diseases?
What are other factors contributing to the spread of these
diseases?
Range of Diseases
Many are Restricted to or more prevalent in tropical and
subtropical zones
More prevalent at lower latitudes, lower altitudes and warmer
temperatures
Warmer conditions promote vectors for disease spread
Range Shifting Vs.
Expanding
In theory parasites should already be in their optimum ranges
If temperatures increase, warming new areas, then the
parasites should be able to move to new territories
But the temperature could also become too hot in some areas
The ranges would shift instead of expanding
Historical ranges included much of Europe and North America
where today malaria is practically absent due to human
intervention
The Other Factors
“Techniques to eradicate malaria have been
Precipitation
available for decades. It is a disease of poverty,
Humidity
not a disease of climate change.”
Ecological
-Plimer
Sociological
Economic
Evolutionary
Mosquitoes
Diseases carried by
mosquitoes are of most
concern
Transfer diseases amongst
humans and animals
Are very sensitive to the
climate they inhabit
Go to the cold to get away!!
So Why the Mosquito?
Mosquitoes thrive in the heat, Bitting more frequently and
reproducing faster
Still water caused by floods and droughts are an excellent
breeding ground for mosquitoes
Winter freezing kills eggs, larvae and adults
Cold limits mosquitoes to seasons or areas where
temperatures stay above certain minimums
Warmer temperatures may enable them to transfer more
diseases for a longer period of time
Eww c’mon More
Mosquitoes?
They carry malaria, dengue fever, yellow fever and encephalitis
Pathogens inside the mosquito mature faster in the heat,
increasing the chance of the disease being spread since
mosquitoes live only several weeks.
Sustained outbreaks of malaria only where temperatures
routinely exceed 60 degrees F
Yellow and Dengue fever only where temperatures rarely fall
below 50 degrees F
What Diseases?
Malaria
Encephalitis
West Nile Virus
Dengue fever
Snail Fever
Yellow Fever
and other insect, rodent and water carried diseases
Malaria
3.3 billion people, half of the world’s population, are at risk of malaria!
It’s the Heat! NO IT’S THE
MALARIA!
The most popular disease mentioned when it comes to the
global warming debate
250 million cases every year, nearly 1 million deaths every year
An average of 1500 cases in the United States reported every
year
Between 1957 and 2009, in the United States, 63 outbreaks of
locally transmitted mosquito-borne malaria have occurred
5th leading cause of death from infectious diseases worldwide
(after respiratory infections, HIV/AIDS, diarrheal diseases, and
tuberculosis).
Poor Countries are most
Vulnerable
In Africa:
89% of the malaria deaths worldwide occur here
One in five childhood deaths are due to malaria
An African child may average between 1 and 6 episodes of
malaria fever each year
10,000 pregnant women die
200,000 infant deaths
Every 30 seconds a child dies from the disease
What Exactly?
Malaria or a disease resembling malaria has been noted for
more than 4,000 years. From the Italian for "bad air," mal'aria
has probably influenced to a great extent human populations
and human history.
The symptoms of malaria were described in ancient Chinese
medical writings as far back as 2700 BC
Malaria is a mosquito-borne disease caused by a parasite.
People with malaria often experience fever, chills, and flu-like
illness. Left untreated, they may develop severe complications
and die.
Curable disease if diagnosed, treated promptly and correctly
Prevent Malaria!
New antimalarials replacing drugs such as
chloroquine that the parasite has become resistant to
Control the mosquitoes
DUH!
Use insect nets,
spray insecticides,
manage breeding habitats
Malaria is basically
eliminated once the per
capita income reaches $3100
Blue is decreasing, red is increasing
Dengue Fever
Mosquito-borne infection found in tropical and sub-tropical regions
around the world, predominantly in urban and semi-urban areas.
Dengue hemorrhagic fever (DHF) is a potentially lethal
complication
The incidence of dengue has grown dramatically around the world
in recent decades. Some 2.5 billion people – two fifths of the world's
population – are now at risk from dengue. WHO currently estimates
there may be 50 million dengue infections worldwide every year.
Medical care treating DHF can decrease mortality rates from more
than 20% to less than 1%
Not quite as widespread as malaria
West Nile Virus
So far in 2010 there has been 39
deaths due to WNV in the united
states
First arrived in North America in
1999
Warmer temperatures, elevated
humidity, and heavy precipitation
increased the relative rate of human
WNV infection in the United States
independent of season and each
others’ effects (Soverow et al. 2009).
Tick-borne Encephalitis
Viral infectious disease involving the central
nervous system that manifests as
inflammation of the brain, the membrane
surrounding the brain and the spinal cord.
Ticks are the vector and rodents are their host
TBE is not dependent on temperature, but
over the last 30 years an impact of climate
warming on the vertical disease distribution in
Central Europe is evident.
Only several thousand cases are reported
annually
Maybe I don’t want to go for that hike after
all...
Killing Corals
Most coral diseases occur at higher sea water temperatures
Coral Bleaching
Black and White Band Diseases
Coral Plague
Aspergillosis
1997–1998, the world's largest
bleaching event ever killed 16% of the
world's reefs
And Annihilating
Amphibians
An estimated 67% of the 110 or
species of Atelopus, which are
endemic to the American tropics,
have met the same fate, and a
pathogenic chytrid fungus
(Batrachochytrium
dendrobatidis) is implicated.
Warmer climates are more
optimum for growth of this
pathogen
Discussion
Global warming can be a factor in increasing distribution and
incidence of infectious diseases
Ranges of these diseases are more likely to shift than expand
Warmer weather is mostly a more suitable environment for
many parasites and the vectors
Non climatic factors are more likely to determine the extent the
infectious diseases spread
Many of the incidences in the United States are due to traveling
Questions?
Literature Cited
Epstein, Paul R. 2000. Is global warming harmful to health? Scientific American
283: 50-57.
Gething, Peter W., Smith, David L., Patil, Anand P., Tatem, Andrew J., Snow, Robert
W., Hay, Simon I. 2010. Climate change and the global malaria recession. Nature
465: 342-345.
Ostfeld, Richard s. 2009. Climate change and the distribution and intensity of
infectious diseases. ecology 90: 903-905.
Pascual, Mercedes and Menno J. Bouma. 2009. Do rising temperatures matter?
Ecology 90: 906-912.
Malaria. 2010. Centers for Disease Control and Prevention. November 2010
<http://www.cdc.gov/malaria/>
J. Alan Pounds, Martin R. Bustamante, Luis A. Coloma, Jamie A. Consuegra,
Michael P. L. Fogden, Pru N. Foster, Enrique La Marca, Karen L. Masters,
Andres Merino-Viteri, Robert Puschendorf, Santiago R. Ron, G. Arturo SanchezAzofeifa, Christopher J. Still & Bruce E. Young. 2006. Widespread amphibian
extinctions from epidemic disease driven by global warming. Nature 439: 161167.
Jonathan E. Soverow, Gregory A. Wellenius, David N. Fisman, and Murray A.
Mittleman. 2009. Infectious Disease in a Warming World: How Weather
Influenced West Nile Virus in the United States (2001–2005). Environmental
Health Perspectives 117: 1049-1052.
Malaria. 2010. World Health Organization. November 2010
<http://www.who.int/topics/malaria/en/>.
Rosenberg, Eugene and Yael Ben-Haim. 2002.Microbial diseases of corals and
global warming. Environmental Microbiology 4: 318–326
Environmental Health Perspectives; John Bruno. "Global warming takes a toll on
coral reefs". 2009. Encyclopedia of Earth. Encyclopedia of Earth. November 2010
<http://www.eoearth.org/article/Global_warming_takes_a_toll_on_coral_reefs?t
opic=49513>
Chavarria, Gabriela, Kim Knowlton, and Dylan Atchley. 2010. The human-climatewildlife nexus. Bulletin of the Atomic Scientists 66: 48-56
Plimer, Ian. Heaven and Earth: global warming the missing science. Lanham:
Taylor Trade, 2009.
Zemana, Petr and Cestmir Beneš. 2004. A tick-borne encephalitis ceiling in Central
Europe has moved upwards during the last 30 years: Possible impact of global
warming? International Journal of Medical Microbiology Supplements 293: 48-54.
Lafferty Kevin D. 2009. The ecology of climate change and infectious diseases.
Ecology 90: 888–900.