Frequency

United States

Kuru does not occur in the United States.

Four cases of BSE, which is a prion disease in cattle, have been reported in the United States. The most recent was reported on April 24, 2012. [26]

Three cases of variant CJD in humans have been reported from the United States. By convention, variant CJD cases are ascribed to the country of initial symptom onset, regardless of where the exposure occurred. There is strong evidence that suggests 2 of the 3 cases were exposed to the BSE agent in the United Kingdom and that the third was exposed while living in Saudi Arabia. [27]

International

Kuru is restricted to the Fore, a people found in the New Guinea highlands, although there is a single report of a case of transmissible subacute spongiform encephalopathy occurring in a visitor to the eastern highlands of New Guinea. [11] Kuru was acquired during endocannibalistic funeral rituals.

When first investigated in 1957, kuru was found to be present in epidemic proportions, with approximately 1000 associated deaths in the first 5 years of observation, 1957-1961. [16] The total number of kuru cases from 1957-2004 exceeded 2700, with more than 200 dying of the disease every year in the late 1950s. This number fell to about 6 per year in the early 1990s and between one and two cases per year in late 1990s, with only 11 cases identified from July 1996 through June 2004. [14] More recently, kuru-related deaths declined to only two from 2003-2008. [16]

The prohibition of the practice of endocannibalism in the 1950s has clearly led to the decline in the epidemic, with a few cases still occurring because of kuru’s long potential incubation period, which can exceed 50 years. [16, 2] Only 9 cases of kuru have been reported among Fore people who were born after 1956, and no cases have been reported among those born after 1959. [14] The last fatality due to kuru was reported in 2005, and no known kuru cases have occurred since then.

However, zoonotic, not human, prion disease, that is BSE continues to be sporadically seen. The BSE epizootic in the United Kingdom peaked in January 1993. There exists strong epidemiologic and laboratory evidence for a causal association between a new human prion disease called variant CJD that was first reported from the United Kingdom in 1996 and the BSE outbreak in cattle. [28]

Mortality/Morbidity

There is no effective treatment for kuru. It is uniformly fatal within 4-24 months of symptom onset. [29] The incubation period may be as short as 5 years or as long as 50 years. [14]

Race

Kuru has affected only the people of the Fore linguistic group of the Eastern Highlands of Papua New Guinea and their neighbors with whom they intermarried. [14, 12, 30]

The practice of endocannibalism was important to the Fore people as a way of respecting their dead relatives. It was rigorously forbidden, however, by the Australian government following the establishment of the Okapa patrol post in 1954 as one of the first administrative controls following contact with the people. Public consumption of dead relatives ceased almost immediately, and compliance was ensured by local police responsible for the subdistrict. By 1956, endocannibalism was effectively eliminated. Surreptitious eating of dead relatives was reported in remote communities for some years afterward, but, by the end of the 1950s, the practice had effectively ended. Epidemiological surveillance for kuru began in 1957 and has continued since. [14]

Sex

During the New Guinea epidemic, kuru was found to predominantly affect women and children of both sexes. Only 2% of overall cases were found in men from 1957-1958. [14]

Age

The latest year of birth recorded for any patient with kuru was 1959; only 9 individuals with kuru are recorded as having been born since 1956. [14] During the peak of the epidemic, it was estimated that most of the affected individuals were young women, but a small number of children and postmenopausal women were found to be infected, as well as postpubertal males in rare cases. [29]

These findings can be explained by women cooking and handling a dead relative's organs and women most commonly consuming the cooked brains. After age 6–8 years, boys were taken from their mothers and raised in the houses of men. From this point on, their exposure risk was the same as that for men, who typically had little participation in these feasts and did not eat cooked brains, by far the most infectious organ responsible for kuru. These cultural practices most likely explain why so few men developed kuru. [14]