The Centers for Disease Control and Prevention (CDC) has identified 220 counties across the United States that are at risk of outbreaks of HIV and hepatitis C from injection drug use.

CDC researchers compiled the list after analyzing factors such as pharmacy sales of prescription painkillers, overdose deaths and rates of unemployment, The Wall Street Journal reports. The 220 counties are located in 26 states.

Most of the 220 counties are rural, and 56 percent are in Kentucky, Tennessee and West Virginia, in the areas of the nation most impacted by the opioid crisis. The other counties are located across the country. The analysis is scheduled to be published in the Journal of Acquired Immune Deficiency Syndromes.

“Our main goal was to prevent this from happening again, and this is one way we think we can help jurisdictions,” said lead author John Brooks, Senior Medical Advisor for the CDC’s Division of HIV/AIDS Prevention.

The CDC urged the affected states to increase testing for HIV and hepatitis C in places frequented by people who inject drugs, and to create plans to respond to potential outbreaks. In Kentucky, Tennessee and West Virginia, officials said they have added more testing and services in communities at risk of outbreaks.

Ardis Hoven, an infectious disease specialist at the Kentucky Department for Public Health, said the CDC analysis showed rural areas not traditionally associated with outbreaks of HIV and hepatitis C are at risk. “Anyone looking at this data should be worried,” she said.