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Cholera
Introduction
In testimony before Congress, the Director of the National Science Foundation indicated that the use of remote sensing technology has allowed scientists to obtain a greater understanding of how global cyclic changes in climate influence the spread of cholera. The disease is an acute infection of the intestines, sometimes fatal. The bacteria produces a toxin that inhibits the absorption of liquids by the body. Cholera epidemics are a serious problem in developing countries lacking pure water and adequate treatment of sewage. Since the cholera bacterium lives in zooplankton, large zooplankton blooms threaten cholera outbreaks.
During an El Niño season, the surface temperature of the ocean (Pathfinder SST data) may rise by as much as 3 degrees Celsius. Warmer waters enhance the growth of a pathogenic microorganism, Vibrio cholerae, that carries the disease. The microorganism is a normal part of brackish water and estuarine zooplankton and phytoplankton, and is often associated with algal blooms. Cholera may infect a coastal population during an El Niño event where a phytoplankton bloom is the vector. Remote sensing technologies have successfully detected, monitored, and quantified phytoplankton concentrations from chlorophyll concentrations (SeaWiFS chlorophyll data) in open oceans and coastal areas.
The 1997-98 El Niño was predicted and monitored for effects.
Disease impacts have only been monitored for one El Niño,
by the Communicable Disease Surveillance and Response (CSR) group of the World Health Organization (WHO),
the Center for Health Applications of Aerospace Related Technologies (CHAART), and others.
Similar results will have to be found in other areas
and for other El Niño events before the findings can be fully embraced by the scientific community.
But there is a strong suggestion that a link exists between El Niño and cholera outbreaks,
making the ENSO phenomenon far more deadly than had been thought.
In 1991, an epidemic in Peru spread quickly through all coastal areas
and even affected mountain and forest regions.
At first blamed on bilge water from a freighter, it was noted that a warmer than usual
El Niño may have produced ecological conditions conducive to the outbreak.
The epidemic cost Peru over $1 billion (U.S. dollars) in lost seafood exports and tourism.
Assisted by poor sanitary conditions, the disease spread throughout South, Central, and North America.
Variations in numbers of cases for 1991-95
reported to the Pan American Health Organization (PAHO) by year and by country
may be related to precipitation changes (TOVS rain data)
(TRMM TMI rain data)
as El Niño was followed by La Niña conditions.
The 1997-98 El Niño also resulted in an outbreak of Cholera as a result of storms and floods.
El Niño Conditions (May 1997 - April 1998)
1 January 1998
Chile
33
N.A.
1 January 1998
Peru
2,863 (in January 1998)
16
1 January 1998
Bolivia
165 (in January 1998)
5
1 January 1998
Honduras
219 (in January 1998)
12
1 January 1998
Ecuador
11 (in January 1998)
1
1 January 1998
Nicaragua
3
N.A.
El Niño-induced flooding in the Horn of Africa in late 1997
was accompanied by increases in cholera, malaria, and Rift Valley fever.
Cholera is endemic in Somalia, United Republic of Tanzania, and Uganda.
The disease normally surges from December through May each year.
The outbreaks tend to recede with the arrival of the annual long rainy season
(TOVS rain data)
(TRMM TMI rain data)
that provides more abundant supplies of safe water.
An El Niño-induced drought would prolong the cholera season.
El Niño Conditions (May 1997 - April 1998)
31 January 1997
Somalia
5,557 (by 30 May)
247 (by 30 May)
31 January 1997
Tanzania 3,000 (by 30 April)
100 (by 30 April)
15 June 1997
Kenya
555
29
1 November 1997
Djibouti
827
29
1 November 1997
Uganda
16,982 (by 24 March 1998)
849 (by 24 March 1998)
1 January 1998
Zimbabwe
335
12
15 February 1998
Rwanda
2,900
55
1 April 1998
Burundi
77
3
Cholera occurs seasonally in Bangladesh.
The 2 annual peaks in the number of cases are variable in size,
and the variability is directly related to climate events.
Numerous cholera cases are observed when the surface elevation of the ocean is high (TOPEX/Poseidon data)
and when the sea surface temperature (SST) (Pathfinder SST data) is elevated.
Little or no cases of cholera were recorded when the surface elevation of the ocean
was low and SST was also low.
This has been shown for retrospective studies of data from Bangladesh for 1978-86
and from Calcutta (India) for 1992-93 (CHAART Research).
Additional compelling evidence exists that the number of cholera cases in Bangladesh rises
about 11 months after the waters of the equatorial Pacific begin to warm.
At a hospital that has tested incoming patients and kept records since January 1980,
the number of cholera cases peaked every 3.7 years,
which is the same frequency of El Niño occurrences.
The 11-month lag has been shown to be due to the time needed first to warm up the local ocean surface waters, and
second for the phytoplankton to respond with rapid growth to a population peak.
In 1998, extremely heavy rainfall and floods contributed to an increase in cholera cases.
Disclaimer:
NASA offers these suggested sites
for additional information regarding Cholera and El Niño - La Niña events.
Web access is required to reach these sites.
Link existence and contents are not under the control of the EOSDIS Science Operations Office.
Date (First Case)
Country
Cases
Deaths
Date (First Case)
Country
Cases
Deaths
6,814 (by 1 Jan. 1998)
4,404 (after 1 Jan. 1998)
252 (by 1 Jan. 1998)
195 (after 1 Jan. 1998)
(including Zanzibar)
40,249 (by 1 Jan. 1998)
11,512 (1 Jan. - 7 June 1998)
2,231 (by 1 Jan. 1998)
321 (1 Jan. - 7 June 1998)
38,697 (1 Jan. - 30 June 1998)
43,911 (by Sept.)
> 1,576 (1 Jan. - 30 June 1998)
1,777 (by Sept.)
