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Indiana HIV outbreak offers lessons about containing local outbreaks and need for harm reduction
Liz Highleyman, 2015-08-10 07:30:00
An early-2015 outbreak of HIV and hepatitis C virus (HCV) in rural Indiana, USA, linked to injection of prescription opiates, offers a good example of how to track and contain a localised outbreak, according to a pair of presentations at a late-breaking prevention research session at the Eighth International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention (IAS 2015) last month in Vancouver, Canada. Attendees at the session stressed that we already know how to prevent such outbreaks and called for implementation of needle exchange programmes and other proven-effective harm reduction measures.
In January 2015, the Indiana State Department of Health, later joined by the US Centers for Disease Control and Prevention (CDC), began investigating an HIV outbreak after disease intervention specialists confirmed nearly a dozen new infections in a rural community in Scott County, near the Kentucky border – a community of 4200 residents that had only reported five cases of HIV during the previous decade. Investigators traced the new infections to people who inject oxymorphone, a prescription opioid or opiate-like painkiller.
The CDC issued an official health advisory about the outbreak in April, and CDC and Indiana investigators published a brief report in the May 1 edition of Morbidity and Mortality Weekly Report.
John Brooks, leader of the CDC's HIV Epidemiology Team, described efforts to determine the source of the Indiana outbreak, trace patterns of transmission, halt further infections and bring affected people into care. He also presented results from a molecular epidemiology analysis of HIV and HCV strains, providing insight into how the viruses spread.
Brooks said that a disease intervention specialist first recognised that two people newly diagnosed with HIV had used the same needles for drug injection; contact tracing soon identified eight more cases. Health officials interviewed newly diagnosed individuals, asking about their use of non-sterile needles, the people they injected with and their sexual partners. People were given the opportunity to suggest any social contacts they thought "might benefit from an HIV test" without naming them as sex or drug use partners. All named individuals who could be located were offered HIV, HCV, hepatitis B virus and syphilis testing.
"It is past time for the federal ban on funding for syringe exchange to end," Steffanie Strathdee
Investigators identified nearly 500 individuals during contact tracing, 83% of whom were located, assessed for risk and tested for HIV. As of 14 June, a total of 170 people were diagnosed with HIV. After a rapid increase in mid-March and April, the outbreak plateaued. "We could tell we were closing in on the epidemic when no contacts named were new," Brooks said.
More than half (55%) of the newly diagnosed individuals were men, all were non-Hispanic white and the median age was 32 years. Among those who were diagnosed with HIV, about 40% reported sharing needles as their only risk factor, 1% reported only sexual risk, another 40% reported both sharing needles and sexual risk, and nearly 20% had unknown risk factors, according to the study abstract.
Almost all newly diagnosed people (96%) reported injection drug use. They described crushing, dissolving and heating extended-release oxymorphone, and some used methamphetamine and heroin as well. The reported daily number of injections ranged from 4 to 15, and the number of injection partners ranged from 1 to 6 per injection event. Interview participants reported that injection drug use in this community is often multi-generational, and family and community members frequently inject together and share syringes and other equipment. The Indiana outbreak reflects a recent upsurge in non-urban injection drug use in the US which has led to increases in acute HIV and HCV infection and overdose deaths.
Some features of this outbreak differ from those of other outbreaks previously seen among people who inject drugs in the US, according to Brooks. The newly diagnosed population was rural, all white, and nearly evenly split between men and women. In contrast, prior outbreaks have traditionally involved inner-city residents, often African-American or Latino, with a 2-to-1 ratio of men to women. But other factors of the Indiana outbreak were similar, including a high rate of poverty (19%), unemployment (9%), low education level (21% without a high school diploma) and limited access to insurance and health care.
Genetic analysis of HIV pol and HCV NS5B gene sequences from plasma samples collected from residents of Scott County and surrounding areas between October 2014 and April 2015 showed that HIV strains were closely related, while HCV strains were more diverse. Usually this type of testing is done retrospectively, Brooks noted, adding that he thought this was one of first times real-time phylogenetic data had been used to inform response to an ongoing outbreak, letting investigators know early on that it was geographically isolated.
There was a single large cluster of related HIV-1 subtype B strains (comprising 55 of 57 tested samples), along with a second very small cluster that Brooks said may represent pre-existing undiagnosed infections. Avidity testing showed that more than 90% of the HIV infections were recent. Phylogenetic trees for HCV were quite different; although three viral clusters were apparent, the "vast majority" of HCV strains did not fall into any of them. Among the 119 samples tested, the most common HCV genotypes were 1a (n = 82) and 3a (n = 29). Almost all people (>95%) diagnosed with HIV had HCV co-infection, while about one-third of samples from people with HCV showed HIV co-infection. Brooks explained that this picture is consistent with HIV newly arriving in a community with a high prevalence of pre-existing HCV of many different types.
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