Behrens-Bradley N, Smith S, Beatty NL, et al. - Three species of kissing bugs (n = 521), which are prevalent household pests in the Desert Southwest of the United States, were captured in or near homes in Bisbee and Tucson, AZ, in order to determine environmental and biological factors accounting for the phenomenon that kissing bugs harboring Trypanosoma cruzi often bite residents of the US Southwest but do not lead to Chagas disease. The most prevalent triatomine in Tucson was Triatoma rubida and in Bisbee, it was T. recurva, whereas T. protracta was exceptional. In Bisbee, 17% and of bugs captured and in Tucson 51.1% harbored T. cruzi. Bite victims (n = 105) revived more than 2,200 bites. Reactions to bites were usual, comprising 32 episodes of anaphylaxis in 11 people. Negative test results for Chagas disease (n = 116) were obtained. The median age of houses was 91 years and 7 years in Bisbee and in Tucson, respectively. Pier and beam foundations were noticed in Bisbee houses. Tucson houses were constructed on concrete slabs. Thus, kissing bugs harboring T. cruzi quickly entered fresh and old homes. Bites of humans led to severe, life-threatening effects. Moreover, no serological evidence of Chagas disease among those bitten was concluded.