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Virginia health officials are investigating the state’s first documented locally acquired dengue virus infection, a case they say is epidemiologically linked to an internationally acquired infection involving a Loudoun County resident.

The investigation was announced Aug. 4 by the Virginia Department of Health. It involves VDH, the Fairfax County Health Department and the Loudoun County Health Department. One dengue patient lives in Fairfax County and the other lives in Loudoun County.

Officials said the locally acquired patient had no known travel outside Virginia before becoming ill. They believe that patient likely became infected through a bite from an infected mosquito after spending time near the person whose infection was acquired internationally. The specific mosquito and transmission event were not directly observed, and the investigation was ongoing.

“There is an initial international traveler who became ill after coming to Virginia, and the other who likely became infected through a mosquito bite while spending time with that individual,” Lucy Caldwell, communications director for the Fairfax County Health Department, said in a statement.

Caldwell said the two cases are epidemiologically connected and that the county health departments are coordinating with VDH.

“Given the two cases are epidemiologically connected, the Loudoun County and Fairfax County Health departments are working together, along with VDH, to coordinate public health efforts,” she said.

Virginia State Health Commissioner Cameron Webb said officials had not found evidence of ongoing spread at the time of the report.

“There is no evidence of continued transmission and no additional reports of locally acquired dengue cases at this time,” Webb said.

Health officials said the risk of contracting dengue in Virginia remains low. Dengue is transmitted through bites from infected Aedes mosquitoes.

The illness can range from an infection without symptoms to severe disease. Symptoms typically last two to seven days. About one in 20 infected people can develop severe dengue, which may cause shock, internal bleeding or death.

CDC data last updated July 29 recorded 1,443 dengue cases nationwide in 2026, including four cases in Virginia. Those figures provide context for the state investigation but do not establish whether the other Virginia cases were locally acquired.

The investigation’s final conclusions were not available at the time of the announcement. Officials also had not reported additional locally acquired cases. The suspected transmission pathway may change as health departments continue their review.