Climate change is exacerbating the risk of potentially dangerous mosquito-borne diseases in California — threatening to turn more of those annoying-but-harmless bites into severe illnesses, experts say. … But officials are now warning of a potential new foe: dengue, a viral infection that in the most serious cases can also lead to life-threatening complications. Until last year, all dengue cases reported in California were associated with people traveling to a country where the disease is common. But Los Angeles County public health officials are now warning about the “unprecedented” local transmission of dengue, which is commonly found in tropical and subtropical climates. … Climate change is contributing to the spread of these invasive, non-native mosquito-borne diseases, experts say. The World Health Organization warned last year that global warming “marked by higher average temperatures, precipitation and longer periods of drought, could prompt a record number of dengue infections worldwide.”