Monday, October 1, 2012

Climate Change and Cholera?

“Thirty years ago, we were ridiculed to even say that the bacterium existed in the environment. But now it is in textbooks. The evidence is so overwhelming, it is understood.” Rita Colwell - University of Maryland cholera expert, and former director of the National Science Foundation

Cholera was originally thought to be a disease purely associated with poor sanitation but recent revolutionary understanding suggest that beyond poor sanitation, other factors such as the environment, hydrology, and weather patterns also come into play (Shah, 2011; Fernándeza et al., 2009)

There is scientific evidence showing a direct influence of inter-annual and inter-decadal climate variability on the epidemiology of vector-borne diseases (WHO, 2000). Climate change has been shown to enhance the spread of infectious diseases two key mechanisms, according to (Epstein, 2011):

1)Global warming expands the geographic conditions conducive to transmission of vector-borne diseases, and
2)Extreme events result in the proliferation of mosquito, water and rodent-borne diseases

A study carried out in Lusaka (Zambia) between 2003 and 2006 analyzed data from three cholera epidemics which occurred in a consecutive fashion. The researchers from the Madrid Carlos III Institute of Health who conducted the study concluded that climatic variables (rain and environmental temperature) are related to the increase in cholera cases during the epidemic period. The results showed that increase in environmental temperature six weeks before the rain season increases the number of people affected by this sickness by 4.9%.

In a study of Vibrio cholera, the bacteria that causes cholera, in the environment, the bacteria was found in water bodies untouched by human waste, its abundance and distribution fluctuating not with levels of contamination, but with sea surface temperature, ocean currents, and weather changes. A 2003 WHO study warned that predicted warming of African lakes, such as Lake Tanganyika, may increase the risk of cholera transmission among local people, and that countries such as Tanzania, Kenya, Guinea-Bissau, Chad, Somalia, Peru, Nicaragua, and Honduras — which suffered major cholera outbreaks after heavy rains in 1997 — may face more cholera epidemics as the climate changes (Shah 2011).

It seems the evidence is becoming so overwhelming. According to Shah (2011) “In Mexico, the abundance of cholera vibrios in lagoon oysters rise as seas warm. In the Chesapeake Bay, Vibrio cholerae levels increase during the summer, as water temperatures spike. In Bangladesh, cholera risk increases by two to four times in the six weeks following a 5-degree C (9-degree F) spike in the water temperature. Likewise, in Ghana, an analysis of 20 years of data revealed a correlation between cholera incidence and rainfall and land surface temperatures. In Djibouti, Somalia, Kenya, Mozambique, and Tanzania, cholera epidemics have been correlated with flooding as well as sea surface temperatures”

As the impacts of climate change on diseases become increasingly prominent, the need to put in place structures and mechanisms to ensure health care systems are well positioned to respond effectively cannot be over-emphasised. How can the health care system, especially in developing countries, respond appropriately to climate change related health risks?

"This is the first time that it has become evident in the sub-Saharan region that the increase in environmental temperature is related to the increase in cholera cases," - Miguel Ángel Luque, Madrid Carlos III Institute of Health

Epstein, P., 2011. Health and Climate Change: 7 Ways You Are Being Harmed in The Atlantic, Sept. 23, 2011 Edition.

Fernándeza, M.A.L., Bauernfeindb, A., Jiménezc, J.D., Gila,C.L., El Omeiria, N., Dionisio Herrera Guiberte, D.H., 2009. Influence of temperature and rainfall on the evolution of cholera epidemics in Lusaka, Zambia, 2003–2006: analysis of a time series. Transactions of the Royal Society of Tropical Medicine and Hygiene. Volume 103, Issue 2. Pages 137–143

Government of Ghana, 2007. National Health Policy: Creating wealth through health. Ministry of Health. Accra, Ghana.

Shah, S., 2011. Climate’s Strong Fingerprint in Global Cholera Outbreaks. Environment360.

World Health Organization Bulletin, 2000. Climate change and vector-borne diseases: a regional analysis. [Accessed: June 19, 2012]