CHARLESTON, W.Va. (AP) — U.S. Sen. Joe Manchin on Monday submitted a congressional inquiry with the Centers for Disease Control and Prevention regarding an HIV outbreak in West Virginia’s largest county.

The West Virginia Democrat asked for the inquiry on behalf of the Kanawha County Commission two months after a CDC official warned that the county’s outbreak was “ the most concerning in the United States.”

Commission President Kent Carper said in a statement that the outbreak “is an important public health issue and is deserving of our full understanding.”

In a letter to Dr. Rochelle Walensky, the CDC director, Manchin asked that the CDC review the commission’s concerns and reply by Friday.

Later Monday, Manchin released a letter from the CDC saying it was eager to meet with public health officials. It said Dr. Jonathan Mermin, director of the CDC’s National Center for HIV-AIDS, would be included in the meeting.

In early February, Dr. Demetre Daskalakis, the CDC’s chief of HIV prevention, gave a presentation at a meeting of a Kanawha County HIV task force.

“It is possible the current case count represents the tip of the iceberg,” Daskalakis said. “There are likely many more undiagnosed cases in the community. We are concerned that transmission is ongoing and that the number of people with HIV will continue to increase unless urgent action is taken.”

The commission’s letter to Manchin asked whether the CDC has completed an official investigation into the county’s HIV surge. The letter said the commission is concerned that the statements referring to the outbreak as the most concerning in the nation “are being made without factual and empirical evidence.”

As recently as 2014, only 12.5% of HIV cases in West Virginia were the result of intravenous drug use. By 2019, 64.2% were, according to state health department data. The increase was due primarily to clusters in Kanawha and Cabell counties.

Kanawha County, which includes Charleston and has 178,000 residents, had two intravenous drug-related HIV cases in 2018. The number grew to 15 in 2019 and at least 35 last year, said Shannon McBee, a state epidemiologist.

By comparison, New York City, with a population of more than 8 million, recorded 36 HIV cases tied to intravenous drug use in 2019, according to the CDC. Counties in other states with populations similar to Kanawha had an average of less than one HIV diagnosis among people who inject drugs, Daskalakis said.

The surge, clustered primarily around the capital of Charleston and the city of Huntington, is being attributed at least in part to the cancellation in 2018 of a needle exchange program that offered clean syringes to injection drug users not able to quit the habit altogether.

Needle exchange programs are included in the CDC’s recommendations for controlling disease outbreaks among intravenous drug users. Such programs exist in dozens of states, but they are not without their critics, including in West Virginia, who say they don’t do enough to prevent or stop drug abuse.

With less than a week left in the regular session, the state Legislature is considering a bill to regulate needle exchange providers.

The nonprofit organization Solutions Oriented Addiction Response provides addicts with clean needles in Charleston and group shares information about HIV testing with residents, including the homeless. SOAR co-founder Sarah Stone has said the legislation could shut down her group’s needle exchange program.

Citing the pending state bill, the Charleston City Council on Monday night postponed voting on a proposed needle exchange ordinance until April 19.