Cases of HIV have skyrocketed in a rural community in the midwestern state of Indiana where 142 people have been diagnosed this year, officials said Friday.

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 Friday 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.