The case follows two local cases reported in 2023, one in Pasadena and the other in Long Beach.
From 2016 through 2018, a dengue outbreak in American Samoa resulted in 660 confirmed cases.
The WHO said Iran's risk is high due to the presence of Aedes mosquitoes and an influx of people from endemic countries.
Two more locally acquired dengue cases have been reported in the Florida Keys.
Children with higher body mass index (BMI) were twice as likely to be hospitalized for dengue than children with lower BMI.
The Americas region has seen a record surge in activity, as travel-linked cases rise and sporadic local cases reported from Florida.
Cases in several Americas subregions are sharply above last year's totals and 5-year averages.
Cross-reactivity among orthoflaviviruses should be considered when testing vaccines against the diseases they cause, the researchers say.
So far this year, 90 countries globally have reported active dengue transmission, with the Americas as the hardest-hit region.
Transmission is increasing in Central America, Mexico, and the Caribbean regions, with cases well above last year at this time.
