Important Gains Made in Global Effort to Control Malaria

A massive scale-up in the distribution of insecticide-treated mosquito nets and other control programs are helping to protect more than half a billion people in sub-Saharan Africa against malaria, according to the World Health Organization. In its latest World Malaria Report, the organization cited these efforts as contributing to significant but fragile decreases in malaria cases and deaths in the region.

Worldwide, the WHO estimates deaths from malaria in 2009 were 781,000, about 200,000 fewer than they were in 2000. The most significant gains were made in Africa, where the disease extracts the heaviest burden on society. There, eleven countries saw cases and deaths drop by at least half between 2008 and 2010. Additionally, in 32 countries outside of Africa where malaria is considered to be endemic–occurring year-round–the number of confirmed cases also dropped by more than half. However, some countries, such as Rwanda, São Tomé and Príncipe, and Zambia showed a worrying reversal to this trend in malaria cases in 2009, highlighting the need for constant vigilance and careful assessment of the roles that socioeconomic and environmental factors, including climate, play in driving these changes.

“The news coming out of the WHO report is overall very encouraging, but we still need to know if any of the changes in malaria trends are really a result of the interventions and not due to other factors, such as a drought,” says Madeleine Thomson, a senior research scientist at the International Research Institute for Climate and Society, which is also a PAHO/WHO Collaborating Centre for Climate Sensitive Diseases. “Knowing this would improve the quality of our impact assessment,” she says.

Climate is an especially important factor in malaria control programs. Seasonal changes in rainfall and temperature may hinder, or aid, the effectiveness of intervention programs. Then there’s longer term climate change, which could work to alter the distribution of malaria in ways that are not yet fully understood.

At the behest of the WHO, Thomson, along with colleagues Pietro Ceccato and Michael Bell, analyzed the relationship between climate and disease trends in a number of African countries for the malaria report. For that rapid fire analysis, the group accessed globally available climate data derived from satellite information and ground-based rainfall and temperature measurements and correlated these results with malaria data at the regional level. They found that for the most part, it is unlikely climate played a major role in the observed changes in malaria trends. However, using the global data sets limited the strength of conclusions that could be drawn at the regional level.

“These data sets tend to be incomplete in regions where ground measurements are sparse and have coarse resolution,” says Pietro Ceccato. “To really get a deep understanding of the relationship between climate and malaria trends, scientists need access to higher resolution, local data sources, which means working closely with national institutions.”

But often the data are not easily available due to logistic, resource and policy constraints.

The IRI has made progress toward this end in Ethiopia, where it collaborates with the Ministry of Health and the National Meteorological Agency to improve decision making on public-health and disease-control issues. In November, the three organizations led a malaria training workshop organized by the Climate and Health Working Group of Ethiopia and funded by The public-health and climate professionals who attended the workshop explored how climate conditions affect malaria distribution. They used local data sets provided by the health ministry and meteorological agency to conduct their analyses. They learned how climate information such as seasonal forecasts and environmental monitoring could help improve predictions of year-to-year variations of epidemics and could be used to more accurately evaluate the role of interventions.

“Taking climate out of the equation is important for malaria impact evaluation,” Thomson says. “Doing this using the national data sets is not only likely to get the best results, but also helps control programs understand the extent to which their outcomes are climate-sensitive. Climate information is another tool in the malaria control toolbox.”

Relevant Links