The incubation period of kuru.
BACKGROUND
Kuru is a transmissible spongiform encephalopathy that was identified in Papua New Guinea in the late 1950s. Several thousand cases of the disease occurred during a period of several decades. Epidemiologic investigations implicated ritual endocannibalistic funeral feasts as the likely route through which the infectious agent was spread.


METHODS
We estimated the incubation period distribution of kuru using a back-calculation model and explored the relation among sex, age at infection, and incubation period. Key assumptions in the model were that the number of new kuru infections in a year was proportional to the number of kuru cases dying that year, and that the epidemic arose from a single case of sporadic Creutzfeldt-Jakob Disease occurring around 1900.


RESULTS
The mean incubation period of kuru was estimated at between 10.3 and 13.2 years. Point estimates of the 90th percentile ranged from 21.1 to 27.0 years. The incubation period in females was estimated to be shorter than that in males. The shortest incubation periods were estimated in adult women, who may have been exposed to the largest doses of infectious material.


CONCLUSIONS
Our findings suggest that the relatively young age of cases of variant Creutzfeldt-Jakob disease probably reflects increased levels of exposure in young people, rather than age-dependency in the incubation period.
Huillard d'Aignaux
Jérôme N
JN
INSERM U360, Hôpital de la Salpêtrière, 75651 Paris Cedex 13, France. jerome.huillard@lshtm.ac.uk
Cousens
Simon N
SN
Maccario
Jean
J
Costagliola
Dominique
D
Alpers
Michael P
MP
Smith
Peter G
PG
Alpérovitch
Annick
A
D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D007729:Kuru / Q000453:epidemiology* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D010219:Papua New Guinea / Q000453:epidemiology; D012307:Risk Factors; D013997:Time Factors