Maine county records largest HIV outbreak in state history as officials point to homelessness and injection drug use

Penobscot County, Maine, has recorded 28 cases of human immunodeficiency virus over the past two years, public health officials said, marking the largest HIV outbreak in the state's history.

The county, home to about 152,000 people, typically reports roughly two HIV diagnoses a year; the recent total represents roughly a seven-fold increase over expected numbers for that period. All but one of the newly reported cases are linked to Bangor, a city of about 32,000 in the county.

Maine Center for Disease Control and Prevention officials said the outbreak is concentrated among people who have experienced homelessness and those who inject drugs. State data indicate that all but one person in the outbreak reported injection drug use within a year of diagnosis, and all but three had been homeless within that same timeframe.

The first positive test linked to the cluster was identified in October 2023, followed by two more in January 2024, the Maine CDC reported. Cases peaked in February 2025, when six were reported in a single month; the most recent publicly released data show two cases in July 2025.

"When we think about the population that’s impacted here, it speaks to all the societal and economic factors that make a population or a community more vulnerable to outbreaks," said Dr. Puthiery Va, director of the Maine CDC. "When the conditions are right, it spreads."

Anne Sites, the Maine CDC's director of infectious disease prevention, said the current cluster is notable for its magnitude and the way cases relate to one another. "If we have had other outbreaks, they may have been different in terms of magnitude — the number of people — or in relation between the cases. But I do believe that this is somewhat of a unique occurrence," she told the Portland Press Herald.

Public health investigators and local authorities have pointed to several factors that likely contributed to the outbreak: an increase in injectable opioids such as fentanyl and heroin in the region, a shortage of stable housing, and disruptions to local health services. In October 2024 the Bangor Health Equity Alliance, which provided clean syringes and HIV testing, closed abruptly, reducing harm-reduction services available to people who use drugs.

Jennifer Gunderman, director of Bangor’s health department, said staffing and resource strains make it harder for local agencies to respond to rising health needs. "Everyone is already sort of overextending in a manageable way. But if our workforce shrinks even more, we’re not only going to lose important resources for the community, we’re going to have less people who can help," she said. "But we can’t say that we can’t address this outbreak. That’s not an option. We have to focus our research and our efforts. There’s no other option here."

HIV is transmitted through certain body fluids, commonly via unprotected sex or sharing needles and syringes. Left untreated, the virus can progress to acquired immunodeficiency syndrome, or AIDS, which severely weakens the immune system and increases vulnerability to other infections. Antiretroviral therapy suppresses viral load, preserves immune function and markedly reduces the risk of transmitting the virus to others.

Nationally, public health data estimate about 1.1 million people are living with HIV in the United States and roughly 38,000 new diagnoses occur each year. Federal figures show about 13 percent of people with HIV do not know their infection status. Latest Centers for Disease Control and Prevention data cited by state officials noted just under 4,500 HIV-related deaths in the United States among people 13 and older in 2023.

State and local authorities said they are continuing case investigations, increasing outreach and encouraging testing, treatment and harm-reduction services to limit further spread. Officials have emphasized that reduced access to health care and prevention services can delay diagnoses and treatment, potentially increasing unrecognized transmission.

The outbreak in Penobscot County underscores the intersection of substance use, housing instability and access to health services in shaping local HIV risk. Public health officials said rapid testing, starting antiretroviral therapy for people with HIV and restoring syringe services and other community-based prevention programs are priorities to contain the cluster and prevent future increases in diagnoses.