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Predicting disease outbreaks in a changing climate

A young girl afflicted with cholera lies in a bed at the crowded St. Nicholas Hospital in Saint Marc, in the Artibonite region of Haiti, where Cuban doctors and doctors with Médecins Sans Frontières are treating those infected UN Photo/Sophia Paris
The world has to get better at prevention and forecasts of climate-sensitive diseases like cholera
Satellite and other new technologies could be deployed to help predict disease outbreaks and give us more time to devise strategies to counteract them, suggests the new Intergovernmental Panel on Climate Change (IPCC) report, which cites examples of how weather information can be used in the battle against deadly pathogens.

In Botswana, it says, an early warning system based on rainfall data forecasts malaria incidence up to four months ahead - malaria outbreaks are associated with inter-annual and seasonal variations. In Singapore a weather-based model for dengue can predict epidemics 13 months ahead of the peak, giving the authorities time to increase control measures

The IPCC report focuses on climate change impacts, adaptation and vulnerability.

NASA scientists say it is possible to predict outbreaks of diseases like Ebola. They have found that outbreaks of the disease coincide with a particularly dry period followed by a sudden very wet season. Satellite data for the Ebola-triggering pattern could serve as an early warning for future outbreaks, they say.

The NASA research is not in the IPCC report, and there is no observational evidence that suggests climate change is increasing the risk of Ebola outbreaks, said Diarmid Campbell-Lendrum, one of the lead authors of the chapter on human health in the IPCC report. But there is a case for "newer approaches such as the use of satellite imagery to give us longer lead times of conditions suitable for transmission. Then we could decrease a lot of health risks from climate change".

Campbell-Lendrum, who is also the climate change and health team leader within the public health and environment department at the World Health Organization (WHO), welcomes the IPCC's spotlight on human health in its new report.

"Newer approaches such as the use of satellite imagery...  give [s] us longer lead times of conditions suitable for transmission"
The obvious direct health risks associated with climate variability, such as the higher incidence of dengue, malaria, cholera and diarrhoea are well-established. But now governments also have to think outside the box, say the scientists because any impact on human health has far-reaching implications.

New concepts

New terms appear in the IPCC report.

In the health context “transitional adaptation” considers focusing beyond the current problems in trying to adapt, to considering how health burdens could be altered and existing interventions affected by a changing climate. The report highlights the example of maintaining food safety standards amid rising temperatures and heavy rainfall. This would require better interaction between human health and veterinary authorities, and the monitoring of food-borne diseases and resources to detect pathogens and contaminants in food.

“Incremental adaptation” includes improving public health and healthcare services for climate-related outcomes like the introduction of vaccination programmes in the USA against rotavirus, “a common climate-sensitive pathogen”, which has helped delay and reduce cases considerably.

Climate change, says Campbell-Lendrum, is having far-reaching consequences for every aspect of life - food, water, air and governance. Higher temperatures have not only affected health, education, food production, energy and water supplies but all these and other sectors have affected each other. Health interventions will have to recognize these inter-sectoral impacts.

Alarming statistics

Alarming figures from WHO’s new study show that seven million people died in 2012 because of air pollution. Another WHO study captured in the IPCC report shows that climate-altering pollutants cost the world US$1.9 trillion every year, taking into account money spent on health interventions. Besides respiratory diseases like asthma, studies have shown a link between air pollution and heart disease and cancer.

The IPCC report shows that ozone pollution is also on the rise, posing a major threat to human mortality. Ozone is a gas, which when present in the upper reaches of the atmosphere protects the earth from harmful radiation but when present near us is harmful. The presence of more warming gases like carbon dioxide (CO2) and methane means more ozone is formed. If CO2 levels are checked, hundreds of thousands of lives could be saved in South Asia, says a study cited by the IPCC.

"The emphasis on adaptation is important, but we would not want to give the impression that we can solve everything through adaptation - we do need to cut emissions, or the resulting ecological damage and health risks will go beyond our ability to adapt," said Campbell-Lendrum. Hence the need for health professionals to have their say on public transport or energy issues.

Atlas, a collaborative effort between WHO and World Meteorological Organization, has been trying to map  the possible spread of diseases like malaria and dengue in a bid to help prevent and/or treat them.

A study cited by the IPCC report showed that by 2050 more than half the world's population, predicted to be 8.5 billion at that time, will be at risk of malaria, which currently kills nearly one million people a year.

The IPCC says the incidence of dengue has increased 30-fold in the last 50 years; and a comprehensive review of research shows that the area of the planet exposed to dengue will increase under most climate change scenarios. In little over two decades, the incidence of diarrhoea will also be up by 8-11 percent in the tropics and subtropics, it says.


This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information: https://shop.un.org/rights-permissions

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