The Drug Enforcement Administration has arrested five alleged drug dealers that it believes helped spark the largest HIV outbreak in Indiana history — a crisis that has prompted a reassessment of the challenges posed by the combination of rural drug use and infectious diseases.

The case has focused on the drug Opana, a painkiller injected by drug addicts in liquid form, according to DEA agent Dennis Wichem. Officials described how at least four of the men are believed to have taken part in selling Opana and meth to individuals in southern Indiana, who then shared needles to inject the drugs, allowing for the spread of HIV. They dated the drug trafficking to as early as October 2014. The HIV outbreak began in mid-December, according to the Indiana State Department of Health.

The state now has 170 cases of HIV, according to public health officials who said in March that a large majority of the cases were due to Opana injection rather than to sexual contact.

"What we have here is an oddity," Wichem told VICE News. "A number of drug addicts in southern Indiana began shooting or injecting Opana, and we've learned by interviewing some of these people that they injected methamphetamine too. But to inject Opana you need a bigger sized needle than normal."

Because Opana requires a large diameter needle to inject the drug, users might have been more likely to share needles. Dr. Beth Meyerson, co-director of the Rural Center for AIDS/STD Prevention and assistant professor at Indiana University School of Public Health, explained to the HIV news site Beta Blog last month that larger gauge needles used to inject Opana can more readily lead to skin abscesses and transmission of HIV and hepatitis C when needles are shared.

The individuals who have been charged include Michael Elkins, John Morgan, Tyler Turner, William Thrower, and Charles Pruett, and the investigation is ongoing.

The DEA alleges that Elkins, who is from Georgia, made bi-weekly trips to Scott County, Indiana, with methamphetamine and also distributed Opana pills there for as much as $160 per pill. They traced the source of his supply to Alabama and Georgia. Morgan was arrested while traveling with Elkins in his truck and was charged with dealing methamphetamine.

Turner and Thrower, both of Indiana, are alleged to have been couriers. They were arrested in Indiana. Authorities arrested Pruett in Georgia this week.

The ongoing health crisis in rural Indiana forced Gov. Mike Pence earlier this year to allow a needle exchange that drug users can use to get clean needles with which to inject drugs.

"In response to a public health emergency, I'm prepared to make an exception to my long-standing opposition to needle exchange programs," Pence said in March.

The state legalized syringe exchange programs under certain circumstances — namely, convincing evidence that an HIV or hepatitis C outbreak is occurring in a defined area and the declaration of a corresponding state of emergency.

Public health officials say that clean needle programs need to be implemented in drug-using areas throughout the United States. Dr. Chris Beyrer, a medical doctor and public health professor at Johns Hopkins University, and Steffanie A. Strathdee, director of the Institute of Global Health at the University of California-San Diego, published an article on Wednesday in the New England Journal of Medicine calling for broader access to the programs.

"When needles are in short supply, injection-drug users have little choice but to share," they wrote. "Given increases in injection-drug use in non-urban communities and the high efficiency of HIV transmission through injection, it was only a matter of time before an outbreak ensued."

Beyrer and Strathdee pointed out that other counties with similar problems in Indiana won't be able to institute a preventative needle exchange program — they will be forced to wait until there is a crisis and a state of emergency is declared. Madison County, in central Indiana, declared a state of emergency earlier this week due to a hepatitis C outbreak that has been tied to drug use.

The epidemic in southern Indiana has frightened public officials throughout the rural US, where health policy experts say drug use and HIV are spreading faster than in urban areas.

"We don't do enough testing or make enough resources available in rural health," Janice C. Probst, director of the South Carolina Rural Health Research Center, told VICE News.

Probst said that lack of access to testing and treatment sites is a major problem. In some states residents may have to travel 250 miles to the nearest HIV testing or treatment center. If they go untested or untreated, it increases the risk of spreading the disease.

"HIV is right now a disease of the disenfranchised, of people who don't get preventative care or education," she said.

And as a matter of public health policy, "if you ignore it, it will become a bigger problem," she said. The federal and state governments should devote more resources to rural programs, as opposed to the traditional urban programs, to try and prevent other outbreaks from occurring and to prevent increased healthcare costs for those infected down the road, added Probst.

Despite calls from the medical community to allow needle exchange programs, there continues to be political opposition to it, including a federal funding ban on programs.

"Permanently lifting the ban on using federal funds to support needle-exchange programs will be a critical component of HIV prevention," Beyrer and Strathdee wrote, "since these programs reduce HIV incidence and front-line exchange workers are often the first people injection-drug users reach out to for help."