They opened the catalogue of a laboratory-supply company to see which one of the 50 human adenoviruses they should order.
"I'd like to say we chose the virus out of some wisdom, out of some belief that it was similar in important ways to SMAM-1," Dhurandhar said. But really, he admitted, it was dumb luck that the adenovirus they started with, Ad-36, turned out to be so fattening.
By this time, several pathogens had already been shown to cause obesity in laboratory animals. With Ad-36, Dhurandhar and Atkinson began by squirting the virus up the nostrils of a series of lab animals -- chickens, rats, marmosets -- and in every species the infected animals got fat.
"The marmosets were most dramatic," Atkinson recalled. By seven months after infection, he said, 100 percent of them became obese. Subsequently, Atkinson's group and another in England conducted similar research using other strains of human adenovirus. The British group found that one strain, Ad-5, caused obesity in mice; the Wisconsin group found the same thing with Ad-37 and chickens. Two other strains, Ad-2 and Ad-31, failed to cause obesity.
The damage is done. Eat less & exercise more.