the stair steps connecting the strands. There are four kinds of base in DNA—molecular components known as adenine, cytosine, guanine, and thymine, and abbreviated as A, C, G, and T, little pieces in the great game of genetic Scrabble. You’ve heard this before on the Discovery channel but it’s elemental stuff that bears repeating, because genetic code is one crucial form of evidence by which disease scientists now recognize pathogens. In the RNA molecule, which serves for translating DNA into proteins (and has other roles, as we’ll see), a different piece called uracil substitutes for thymine, and the Scrabble pieces are therefore A, C, G, and U.
Singh and Cox-Singh, with the help of Radhakrishnan, were looking for DNA and RNA fragments characteristic of Plasmodium parasites generally—and they found some. But these fragments hadn’t come from P. malariae, nor from P. vivax nor P. falciparum either. They represented something new—or, anyway, something less expected and familiar.
Further testing and matching showed that five of the eight Kapit patients were infected with Plasmodium knowlesi. And there was no clustering of cases within a single longhouse, another unexpected clue. The absence of clustering meant that these people hadn’t passed the parasite, via mosquitoes, to one another. Each patient seemed to have caught it from a mosquito that had bitten a macaque.
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The Faculty of Medicine and Health Sciences, University of Malaysia Sarawak, resides in a sleek high-rise just ten minutes by cab from the big new hotels and the old market buildings of the Kuching riverfront. I found Balbir Singh there in his office on the eighth floor, a handsome and genial fiftyish man surrounded by books and papers and golf trophies. He wore a dark beard going gray, a purple-black turban, and a pair of reading glasses dangling around his neck. Despite the fact that he and his wife were leaving town the next day, for meetings with health officials elsewhere in Borneo, they had agreed to give me some time. Their discovery of P. knowlesi among the people of Kapit was still rather fresh, with implications for malaria treatment throughout Malaysia and beyond, and they were glad to talk.
From the high-rise, Balbir Singh and I walked across the street to a very modest South India café, his favorite, where he bought me a biryani lunch and told me about his Punjabi Sikh grandfather who had emigrated to Malaysia and his own circuit through Liverpool. I heard about P. knowlesi living successfully, asymptomatically, in long-tailed macaques amid the forest canopy. I heard about some surveyor, a spy, out in the Malaysian forest somewhere, but the information was flying and the food was good and I could hardly make sense of that part until later. Back in his office, Singh recounted with great élan the story of Julius Wagner-Juaregg and malaria pyrotherapy for syphilitics, Professor Ciuca’s adaptation of Plasmodium knowlesi for that purpose in Romania, and again the mysterious American surveyor who got infected with this monkey disease in the wild. Singh showed me photos, on his computer screen, of Iban longhouses along the upper Rajang River. Eight different ethnic groups, but mostly Ibans, he said. Here’s a longhouse, accommodating anywhere from five families to fifty. Great for doing blood surveys—you don’t have to travel from house to house. Here’s another typical scene: You see that greenery, you think it’s grass, right? But it’s not grass, it’s hill paddy. Rice. They also grow corn. At harvest time the people stay out at night in huts by their fields, trying to haze off the macaques that come to raid the crops. They don’t shoot the animals, because bullets are too expensive and a long-tailed macaque offers very little meat. Also, in some of the longhouses there’s a taboo: Kill a monkey and its spirit will visit the womb of your pregnant wife, with dreadful effects on the baby. The monkeys are bold and persistent, and they’ve got to be kept off the paddy rice—evidently a matter of arm waving, shouting, clanging of pots. Two nights, three nights in a row the people stay out there. Of course they get bitten by nocturnal forest mosquitoes, including Anopheles latens, the main insect transmitting P. knowlesi hereabouts.
“So control is a problem,” he said. “How are you going to control this?” Both men and women are infected. Their livelihood depends on going into the forest, where the macaques are abundant and so are the mosquitoes.
He showed me blown-up images from microscope slides full of malaria-infected human cells. Circles and dots,