Global Policy Forum

Climate Change Brings New Diseases


By Julio Godoy

June 19, 2009


As its name suggests, the West Nile virus, a leading cause of a form of meningitis and a neuro-invasive disease, has until recently been reported mostly in tropical and sub-tropical African regions. But it is now about to become a global virus.

"Due to climate change, regions with moderate temperatures, that is most of Europe and North America, are now facing diseases that were thought completely exotic in these areas," says Thomas Mettenleiter, president of the German Federal Research Institute for Animal Health, also known as the Friedrich- Loefller Institute (FLI), based in the Riems, a Baltic Sea island 200 km north of Berlin. About 100 health experts who gathered at Riems last month for a conference on health challenges posed by climate change and globalization agreed that the spread of disease was no longer only through air and sea travel. The acceleration of climate change has created conditions for these vectors, mostly mosquitoes, but also rodents and other species, to settle in habitats formerly inappropriate for them.

"Since the end of the last great ice age some 10,000 years ago, the average European temperature has risen by six degrees Celsius," says Horst Aspoeck, head of the department of medical parasitology at the University of Vienna. This regional warming accelerated sharply after industrialization began some 200 years ago, Aspoeck said. "For this century, we have to fear a new, rapid temperature jump of at least three degrees Celsius in Europe."

"In recent months, numerous cases of WNV (West Nile Virus) infections have been reported in Austria, Hungary, and Bulgaria," said Mettenleiter from the FLI. "For Germany, this means that the West Nile Virus is already at our doorsteps." The virus has been reported already in the United States. A total of 3,630 cases of WNV neuro-invasive disease (WNND), including 124 deaths, were reported in the country in 2007, according to the U.S. Federal Centre for Disease Control and Prevention. The disease was first identified in New York in 1999, and has now spread across the country to reach California.

Virologists expect a similar spread of the yellow fever mosquito, which can transmit diseases such as dengue, chikungunya, and yellow fever. "It is only a matter of time before the yellow fever mosquito becomes domestic in Spain, and with it maybe dengue and yellow fever," says Matthias Niedrig, a virologist at the German Robert-Koch-Institute for health research.

Lyle Petersen, director of the U.S. division of vector-borne infectious diseases at the National Centre for Zoonotic, Vector-Borne and Enteric Diseases, and who in 2003 contracted the WNV, observed the virus's transmission speed under different temperatures. Under average temperatures of 17 degrees Celsius, it took 30 days before the infected mosquito transmitted the virus. By the end of the period, most of the mosquitoes observed had died - it was too cold for them to survive. But if the average temperature was 30 degrees Celsius, it took only five days for the transmission because thanks to the warm temperatures, most mosquitoes survived.

In some cases, however, apparently negligible temperature changes suffice to spark a pandemic. In 1997, an observed rise of 0.5 degrees Celsius in the surface of the Indian Ocean waters provoked a massive outbreak of the Rift-Valley fever in East Africa. The warmer waters provoked heavy rains, and the high temperatures, the humidity and inadequate rainwater drainage created the perfect incubation conditions for mosquitoes transmitting the virus.

The virus first killed hundreds of thousands of goats and sheep in Kenya, Somalia and Tanzania, provoking a famine in the region - without goats and sheep, the peasant population had less to eat. But then, humans contracted the virus. According to the World Health Organization, several hundreds died of diseases caused by the virus in the three countries.

The Rift-Valley virus case in Eastern Africa shows how climate change is threatening public health in developing countries. Compounded with rapid, uncontrolled urbanization and insufficient public hygiene, climate change is creating conditions for the return, or the worsening, of diseases thought to be under control, according to a report by the University College London (UCL) and the medical journal The Lancet.

The report, titled 'Managing the health effects of climate change', says that climate change is now the biggest health threat globally, especially in developing countries. "The epidemiological outcome of climate change on disease patterns worldwide will be profound, especially in developing countries where existing vulnerabilities to poor health remain." The report says the urban population in developing countries is projected to increase from 2.3 billion in 2005 to 4 billion by 2030, and this will be accompanied by an expanding urban sprawl and poor housing. "This change will inevitably increase the risk of heat waves and heat strokes in cities in developing countries as a result of the so-called heat island effect." The heat island effect refers to the significantly higher temperatures observed in metropolitan areas, compared with their surrounding rural areas, and caused by the modification of landscape and by waste heat generated by the massive use of energy in the cities.

The report's lead author, Anthony Costello of the UCL, told IPS that "the failure to act (to stop climate change) will result in inter-generational injustice, with our children and grandchildren scorning our generation for ignoring the climate change threat - with similar moral outrage to how we today look back on those who brought in and did nothing to stop slavery."


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