Global warming could also lead to U.S. outbreaks of infectious diseases that are currently confined to more tropical countries. For example, local transmission of malaria could become possible in much of the U.S. by the middle of the next century. As travelers already bring several cases of malaria into the U.S. each year, local epidemics are possible. Recently 13 cases of dengue fever have been confirmed in and around McAllen, Texas. Dengue has recently reemerged in Central America and spread in Mexico.
Local transmission is suspected in the Texas cases, but is difficult to confirm.