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NATURE|Vol 441|29 June 2006 NEWS

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Some people in Papua NewGuinea who once feasted ontheir own relatives did notsuccumb to the prion diseasekuru until 50 years later, sayresearchers who havelaboriously tracked down thelast sufferers in remote villages.The discovery renews concernthat another human priondisease, variant Creutzfeldt–Jakob disease (vCJD), might beincubating silently in somepopulations and could rear itshead decades from now.

Neurologists have long beenfascinated by kuru, whichcaused an unprecedentedepidemic of neurodegenerativedisease in the Fore people ofPapua New Guinea that peakedin the 1950s and early 1960s. Indeath rituals, families steamedand ate the bodies of theirrelatives — along with, it waslater discovered, infectiousprion proteins that caused thedebilitating and fatal disease.The ritual was prohibited in themid-1950s by the Australianauthorities who governed thatpart of Papua New Guinea, andthe disease eventually becameless frequent.

Interest in kuru reawakenedwith the realization that vCJD,

transmitted from cows infectedwith bovine spongiformencephalopathy, might cause asimilar epidemic among thosewho ate infected meat in the1980s and 1990s. So far, only156 deaths from vCJD havebeen reported in Britain, theworst-affected country, and thenumber of new cases peaked in2000, suggesting that vCJDtakes about ten years toincubate. But debate continuesabout whether another wave ofcases could yet appear.

John Collinge at UniversityCollege London and hiscolleagues went to Papua NewGuinea to find out. Most peoplewith kuru have already died, butthe team ramped up existingdisease monitoring to find thelast of the epidemic. Workingwith local communities, theyscoured isolated villages thatare typically more than 2,000metres above sea level, lost indense rainforest and connectedonly by tracks. “It’s arduoustrekking,” says Collinge.

Between 1996 and 2004, theresearchers found what theybelieve are the last 11 cases ofkuru. Patients’ histories werecollected, to piece togetherwhen they were probably

infected. The longestincubation time was calculatedto be at least 56 years, andperhaps seven years longer —although the averageincubation time seems to be 12years (J. Collinge et al. Lancet367, 2068–2074; 2006). “Forthe first time we can see theextraordinary incubationperiod in human prion disease,”says Collinge. “It’s soberingthat, half a century on, thisdisease has not disappeared.”

Collinge says that vCJDcould have a much longeraverage incubation time, of 30 years or more, because theprions are passing from cows to humans rather than betweenhumans. A species barrierextends incubation times inanimal tests. People who havealready succumbed to vCJDmight have been particularlygenetically susceptible, asother evidence has suggested.

Mathematical models usedto predict the size of a vCJDepidemic could now includethese findings. “Most peopleseem to think we’re over theworst,” Collinge says. “We haveto be cautious about assumingthis disease is going away.” ■

Helen Pearson

Experts comb tropics for clues to vCJD

known as the hockey stick, and was featuredprominently in the executive summary forpolicy-makers in the 2001 report on globalwarming from the Intergovernmental Panelon Climate Change (IPCC).

Shortly after it appeared in the report, twoCanadians, economist Ross McKitrick andmineral-exploration consultant StephenMcIntyre, attacked the methodology behindthe graph, claiming that it was based oninsufficient data and flawed statistical analy-sis. US politicians amplified their com-plaints, most prominently RepresentativeJoe Barton (Republican, Texas), who in 2005wrote to Mann demanding he share his datawith critics and congressional overseers. Inan effort to quell the controversy, the chair-man of the House Committee on Science,Representative Sherwood Boehlert (Repub-lican, New York), commissioned the acad-emy to examine the earlier work.

The academy essentially upholds Mann’sfindings, although the panel concluded thatsystematic uncertainties in climate recordsfrom before 1600 were not communicatedas clearly as they could have been. The NASalso confirmed some problems with the statistics. But the mistakes had a relativelyminor impact on the overall finding, saysPeter Bloomfield, a statistician at North Carolina State University in Raleigh, whowas involved in the latest report. “This studywas the first of its kind, and they had tomake choices at various stages about howthe data were processed,” he says, addingthat he “would not be embarrassed” to havebeen involved in the work.

Panel members were less sanguine, how-ever, about whether the original workshould have loomed so large in the executivesummary of the IPCC’s 2001 report. “TheIPCC used it as a visual prominently in thereport,” says Kurt Cuffey, a panel memberand geographer at the University of California, Berkeley. “I think that sent a verymisleading message about how resolved thispart of the scientific research was.”

“No individual paper tells the wholestory,” agrees North. “It’s very dangerous topull one fresh paper out from the literature.”

Mann says that he is “very happy” withthe committee’s findings, and agrees withthe core assertion that more must be done toreduce uncertainties in earlier periods. “Wehave very little long-term information onthe Southern Hemisphere and large parts ofthe ocean,” he says. As for the report’s effecton the policy debate, Mann says: “Hopefullythis is the beginning of us, as a community,putting that silliness behind us.” ■

Geoff Brumfiel

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