The Heat Is Online

Scientists Identify Provisional Link to Altered Rainfall and Plague Outbreaks

Changing rainfall linked to plague outbreaks - report, July 25, 2011

LONDON (AlertNet) – Outbreaks of the plague – a relatively rare but deadly disease – are linked to rainfall and may become more frequent in some areas as climate change alters weather patterns, scientists from Norway and China say.

In a research project, Norwegian and Chinese scientists analyzed data from the last major outbreak of plague, which originated in China around 1855 and lasted over 100 years. The researchers compared the number of cases per year between 1850 and 1964 against the level of rainfall in that and the preceding year.

“We have found a very clear relationship between the amount of precipitation and the occurrence of human plague,” said Nils Stenseth, a co-author of the study and chair of the Centre for Ecological and Evolutionary Synthesis at the University of Oslo.
However, he said that while a plague pandemic would be unlikely now because of advancements in medicine, he does think that long-term changes in the climate could increase plague outbreaks in the coming decades.

“It’s a very serious disease. It won’t be a huge number of cases, but it will be occasional cases and occasional families that will catch this disease, so I think doctors should be alert that this might happen so they can properly diagnose the disease,” he said.
Historically, the plague has been devastating, most famously claiming the lives of at least 30 percent of Europe’s population during the Black Death of the mid-14th century, after the disease arrived from China. Much of its danger comes from how fast-acting it is; if left untreated, most affected people die within a few days.

Researchers around the globe are attempting to predict the effects of climate change on human health, including how it may impact the spread of diseases such as malaria, Lyme disease and West Nile virus. Plague is transferred from an animal host, typically rodents, to humans by the bite of infected fleas.

A report written last year by the Interagency Working Group on Climate Change and Health  - a collaboration that includes representatives from the U.S. Departments of Agriculture, State, Health and Human Services as well as the National Institute of Environmental Health Sciences and many others - analyzed the potential impacts of climate change on human health.
More worryingly, “disruption of economies, transportation routes, agriculture, and environmental services could result in large-scale population movements within and between countries, as well as a general decrease in what are now considered minimum standards of living,” it said. As a result, “a severe degradation of rural and urban climate and sanitation conditions could bring malaria, epidemic typhus, plague and yellow fever to their former prominence.”

The researchers who analyzed the Chinese data hypothesized that the wetter climate made food more abundant for rodents, causing a growth in their population, with consequences for the spread of plague among humans.
“People should be alert,” he said. “It’s not reason to make this very dramatic … but a few cases is serious enough.”