Meanwhile, Michael Alpers, who had been studying kuru since 1961 and who had taken time out from his own field work to collaborate with Gajdusek and Gibbs on the NIH primate study, waded through six years of Gajdusek’s epidemiological data on the Fore. After examining hundreds of Fore genealogies, he and Gibbs came up with a remarkable observation: Instances of kuru were beginning to decline in children, starting with the youngest age group. The question immediately became, “Why?” Shortly after conferring with Robert Glasse and his wife, Shirley Lindenbaum, Alpers came up with a hypothesis.
According to information gathered from interviews with the Fore, kuru victims were favored at mortuary feasts because the physical inactivity that characterized the latter stages of the disease left the stricken individuals with a tasty layer of subcutaneous fat. Starting in the 1950s, though, government authorities in New Guinea began cracking down on the practice of ritual cannibalism, and with mortuary feasts now forbidden by law, fewer people were eating infected tissue. As a result, incidents of the disease were decreasing. Additionally, since kuru had a shorter incubation period in children than it did in adults, the reduced occurrence of ritual cannibalism translated swiftly into a decreased incidence of kuru in the youngest sector of the population.
In a February 1966 article in Nature, Gajdusek, Gibbs, and Alpers described the experimental transmission of a “kuru-like syndrome” to their chimpanzees although the identity of the disease-causing agent was still unknown. Gajdusek, who still believed that they were dealing with a slow virus, was also reluctant to attribute the transmission of kuru to the consumption of infected flesh. Instead, he supported the view that during the process of handling and cutting up the dead, the kuru-causing agent was transmitted via cuts or across the thin mucous membranes that line the human mouth, eyes, and nose (a form of exposure known as inoculation).
By 1973, however, Gajdusek had come around to the idea that inoculation and consumption were both viable routes for kuru transmission.
The mechanism of spread of kuru is undoubtedly contamination of the population during their ritual cannibalistic consumption of their dead relatives as a rite of respect and mourning. They did the autopsies bare-handed and did not wash thereafter; they wiped their hands on their bodies and in their hair, picked sores, scratched insect bites, wiped their infants’ eyes, and cleaned their noses, and they ate with their hands.
Other researchers, like Joe Gibbs, stuck to the hypothesis that Fore mortuary practices, rather than the actual consumption of infected flesh, were the primary routes of kuru transmission. In a 2002 interview, the NIH researcher admitted that initial attempts to transmit kuru to chimps via a gastric tube (which modeled the consumption of infected flesh by humans) had failed, and that it was only after injecting the animals with liquefied brain material from kuru victims that they came down with the disease. As for how kuru was transmitted to the Fore, Gibbs explained that the Fore had multiple routes of inoculation, including their eyes and mouths, as well as skin lesions caused by leeches, mosquito bites, and the razor-sharp blades of puni grass.
Today, in regions of West Africa, the Ebola virus is often spread because of ritual practices that involve handling of recently deceased Ebola victims. For example, some Muslims believe that family members should wash the bodies of the dead, a practice that also includes the elimination of certain bodily fluids. When performed under less-than-sanitary conditions, this ritual can place individuals in grave danger if they come into contact with infectious body fluids like blood, vomit, and diarrhea—all of which characterize the advanced-and end-stage symptoms of Ebola.
I asked Shirley Lindenbaum if she thought that Fore mothers had encouraged their children to handle the dead during mortuary ceremonies.
“Mothers handed food to their small children to eat,” she said. “Since people eat with their hands, most children would touch the food given to them by their mothers and other female relatives. Children would not have been involved in the cutting of bodies, though one of my interpreters remembered sitting with others watching his mother being cut [up] and eaten. So, just as with adults, handling the food was one possible one route of infection, but as I recall, this depended on cuts and scrapes that allowed the infectious agent to enter the bloodstream—which the rest of us agree could not explain the dimensions of the epidemic. That would require a lot of cuts and scrapes, an unlikely scenario.”