Could plague make a comeback with climate change?

It sounds like scaremongering – putting together in one sentence what is widely considered the chief global threat of our time, and historically one of the most feared diseases.

But there is evidence of a correlation. The link was made, not for the first time, with a statistical time-series analysis of extensive data from Kazakhstan in a paper published last week, which I covered with a news story that appears on the Forum’s website [PDF]. It showed a correlation between plague prevalence and wetter, warmer conditions in spring.

Four years ago a study by researchers from the same group, led by Nils Stenseth of the University of Oslo, described an association between climate variations in the Central Asia region and plague patterns in great gerbils. Their current work takes things a step further, mainly by showing a relationship with human cases of the disease, not just prevalence in animals.

Although the findings aren’t conclusive the authors say plague should be monitored more closely in Central Asia – a note of caution echoed by Tony McMichael, whose commentary was published alongside the paper. McMichael told me that current climatic changes are “at least as great” as those captured in the analysis.

The paper caught my eye because of the recent outbreak of plague in northern Peru, the first since 1994. I asked McMichael whether climate change could have played a role there. He said the ecological dynamics in South America might be different from Central Asia, but rodents would probably react in the same way to changes in climate and the availability of food.

Since it’s a greater prevalence of plague in rodents that comes first after climatic change, causing a ‘spill over’ of the disease to nearby human populations, I’d be interested to see if an analysis crops up of climatic fluctuations and plague in animals in Peru. That’s if decades’ worth of good data are on hand.

A few studies have already made the link in North America. The latest one, described in a paper published this month, again by Stenseth and colleagues, finds evidence that El Niño Southern Oscillation and Pacific Decadal Oscillation combined have an influence on the pattern of human plague cases reported in the Western US over 55 years.