Around 142 people have been tested positive for HIV this year among the rural community in the midwestern state of Indiana. Pregnant women, grandparents, their adult children and grandchildren are among the new cases of HIV linked to illicit injections of oxymorphone, a potent prescription painkiller.
Scott County, a community with a population of 4,200 people and just one doctor in southeastern Indiana, previously saw no more than five cases of the virus diagnosed in one year, health authorities said.
From 2009-2013, the county recorded just three new cases of HIV, said Indiana State Health Commissioner Jerome Adams, describing the current outbreak as "unprecedented."
"We literally have new cases being reported every day, literally on an hourly basis," Adams told reporters.
A public health emergency was declared in Scott County on March 26 by the state governor.
The US Centers for Disease Control and Prevention on April 24 issued a nationwide alert to health care providers to be on the lookout for similar outbreaks of hepatitis C and the possibility of future human immunodeficiency virus among injection drug users.
"At this point there is no sign that infections are increasing on a national level among people who are injecting drugs," said Jonathan Mermin, director of the National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention.
But, he added the situation in Indiana "should serve as a warning that we cannot let down our guard against these deadly infections."
About 3,900 new HIV infections per year in the United States are linked to injection drug use, down from a peak of 35,000 annually in the late 1980s when heroin use was driving the infections among needle-sharers, he said.
Heroin is less popular these days but prescription painkiller abuse is on the rise in the United States, where opioid poisoning deaths have nearly quadrupled from 2009 to 2011.
Scott County has an unemployment rate of 8.9 percent, "a high proportion of adults who have not completed high school (21.3 percent), a substantial proportion of the population living in poverty (19 percent)," said the CDC's Morbidity and Mortality Weekly report.
Four out of five of the diagnosed cases have admitted to injecting drugs, health authorities explained during a conference call with reporters.
Their drug of choice is an oral painkiller known by the brand name Opana that they crush and dissolve, even though it is sold in an abuse-deterrent form.
They may shoot up as often as every four hours, and are using and sharing larger needles than heroin users typically do, raising their risk of exposure to HIV.
The problem of painkiller addiction in the area began more than a decade ago, said Joan Duwve, chief medical consultant for the Indiana State Department of Health.
"Many family members will use drugs together," she said.
"There are children and parents and grandparents who live in the same house who are injecting drugs together, sort of as a community activity."
The age range of those infected so far is 18-57. Just over half are men. Seven percent of the female patients have identified themselves as commercial sex workers, the CDC said.
The CDC said interviews showed each person reported sharing needles with an average of nine other people.