Nine different viruses have been implicated in obesity in animal models,but their role in human obesity has not been established conclusively.Avian adenovirus SMAM-1 is the first virus to be implicated in human obesity.hAd-36 has been found to be more prevalent in obese humans.Chickens inoculated with hAd-37 had much more visceral fat and body fat.Rous-associated virus type 7 induces a syndrome in chickens characterized by stunting and obesity,clearly,not every case of obesity is of infectious origin.However,if a few pathogens can cause obesity,there may be more awaiting discovery.These data give a new perspective to the etiology of obesity and raise the possibility of infection as a contributing factor for obesity in some humans.When such a relationship between pathogens and human obesity is well established,vaccines or antimicrobial agents may be employed to prevent or treat some forms of obesity.