Can 'seek and treat' strategy stop HIV epidemic among injection drug users?

Seeking a "tipping point" toward elimination

Even 20-plus years into the North American HIV epidemic among injection drug users (IDUs) it is theoretically possible to eliminate the epidemic, dramatically cutting transmission among this at-risk population, researchers are finding.

A study found that highly active antiretroviral therapy (HAART) expansion through the Seek and Treat program of the British Columbia Centre for Excellence in HIV/AIDS is effective in controlling HIV epidemics among injection drug users. Moreover, with earlier treatment initiation it may eliminate HIV completely.1

The key is to target the IDU population with a comprehensive program that people who have an unknown serostatus, test them regularly, and get them into early antiretroviral therapy if they're HIV positive and medically eligible for treatment.

"First and foremost, our study reinforces the critical importance of making treatment available after diagnosis is made," says Krisztina Vasarhelyi, PhD, an adjunct professor at Simon Fraser University in Brunaby, Canada, and coordinator of IMPACT-HIV Project at the British Columbia Centre for Excellence in HIV/AIDS. IMPACT stands for Interdisciplinary Modeling for the Prevention And Care and Treatment of HIV.

"Early treatment will help prevent the transmission of HIV and lower the incidence in the community," she adds.

The Seek and Treat strategy as well as the Treatment as Prevention concept was developed by Julio Montaner, MD, and coworkers at the B. C. Centre for Excellence in HIV/AIDS.

"What the models show is that we can wipe out HIV in the injection drug using community," says Alexander Rutherford, PhD, scientific director of the Complex Systems Modeling Group at the Centre for Interdisciplinary Research in the Mathematical and Computational Sciences (IRMACS) at Simon Fraser University. Rutherford also is an adjunct professor in the mathematics department at the university.

"It's an idealized picture of the real world, and it doesn't capture everything about the IDU community, but it tells you that Seek and Treat can have the right impact," he adds.

"What we have discovered in a lot of these models of IDU epidemics is if interventions are applied beyond a certain threshold then we reach a tipping point, and the tendency of the epidemic is to go toward elimination," Vasarhelyi explains.

Targets elusive population

Vasarhelyi, Rutherford, and co-investigators looked at the potential impact of British Columbia's $48 million, four-year pilot project called Seek and Treat. The program targets hard-to-reach populations, including injection drug users. Case workers and other professionals seek out people to bring into testing and then refer HIV-positive, medically eligible individuals to HIV providers and other resources.

Using a network model, investigators mathematically defined target individuals and key parameters, such as syringe sharing frequency that results in HIV transmission, Rutherford says.

The model addresses social influence in which individuals take up behavior that is similar to their peers, he adds.

"We try to capture the interface between disease transmission and behavior strategies," Rutherford says.

The Seek and Treat concept ties into the concept of using treatment as a means of preventing HIV transmission, particularly among marginalized communities that have difficulty accessing care, Vasarhelyi says.

Even though health care, including HAART, is available for free to people in British Columbia, there are many individuals with the disease who are not engaged in care, she notes.

"Universal health care is not enough; there are large numbers of people who clinically are eligible for HIV treatment, and they are not receiving it in Canada," she adds.

"These include sex trade workers, homeless people, injection drug users, and others," she explains. "The idea is to go out into the community and offer people rapid HIV testing and engage those who test positive in care and treatment."

More than 5,000 people are on HAART in British Columbia, where the epidemic is concentrated primarily among men who have sex with men (MSM), injection drug use, and sex workers. This number is expected to increase as Seek and Treat, which started earlier this year, begins to have a positive impact on engaging more people in care.

The impact likely will include reduced rates of AIDS-defining illness, and result in a reduction of emergency room use and hospitalizations, Vasarhelyi says.

"We're looking at what would be the impact of HAART expansion on health care costs and utilization," Rutherford says.

From a public health perspective, the widespread use of HAART among a marginalized population could have a big impact on reducing transmission rates.

"There have been different mathematical models that show the use of HAART lowers community viral load, and, in doing so, very much lowers the risk of infection," says William McColl, political director of AIDS Action in Washington, DC.

"It creates the possibility or potential of lowering infection rates to such a low level that you can contain the epidemic," McColl says. "One of the groups that has been doing a lot of work on that concept is Project Inform in San Francisco, California."

CDC pursuing strategy

Also, the Centers for Disease Control and Prevention (CDC) in Atlanta, GA, has a test and treat initiative for the U.S. population as a whole.

Targeting a specific marginalized population with this strategy is a way to provide a functional cure, McColl notes.

"What we realize with this mathematical model is we have the means within our grasp to roll back and contain the epidemic," he adds. "The road is long and hard, and it's difficult to provide HAART to everyone, but the long-term implications are extremely exciting."

In the United States, the federal government's policy change last December of removing the ban on the use of syringe exchange programs could have a positive impact on reducing the HIV epidemic among injection drug users, as well.

"HIV organizations, civil rights organizations, and even substance abuse organizations have been calling for the implementation of syringe exchange for 20 years," McColl says.

"It's been a lost opportunity, and probably tens of thousands of people who contracted HIV through this method and the corresponding deaths could have been averted with a fast government response," he adds. "Instead, we've had dithering for 20 years."

Unfortunately, even the Congressional action to remove the ban on syringe exchange was not followed by action to increase funding for such programs, he notes.

"It looks to me like there is little or no funding going out with the Fiscal Year 2010 funding," he adds.

Still, the ban's elimination likely will result in more local authorities deciding to fund such programs.

"It should have happened 20 years ago, but it's a positive step forward," McColl says.

Reference

  1. Bastani P, Hogg RS, Marshall B, et al. Highly Active Antiretroviral Therapy eliminates HIV epidemics in a network model of an injecting drug user community. Poster presented at the 2010 Conference on Retroviruses and Opportunistic Infections (CROI), held Feb. 16-19, 2010, in San Francisco, CA.