What Is HIV Contact Tracing and Why Is It Important?
HIV contact tracing, also sometimes called HIV partner notification, is the practice of identifying, locating and informing someone that a partner they have had sex or used drugs with has been diagnosed with HIV. Contact tracing is meant to encourage the partners to test for HIV to identify new HIV infections as early as possible.
This article will review what is known about the acceptability and effectiveness of contact tracing strategies and provide a snapshot of new technologies and promising approaches used for contact tracing in Canada.
Why Is HIV Contact Tracing Important?
Research tells us that the risk of passing HIV on to others is substantially higher during the first few months of HIV infection. Some research suggests it can increase the risk by as much as 2500%.1-3 This means that early identification of HIV infection, combined with effective prevention counselling, should help to reduce the transmission of HIV. We know that when someone learns of their HIV status, they typically take measures to prevent transmitting HIV to others.4 Contact tracing is an important tool to identify people in the acute stages of HIV infection. Finally, we also know that effective linkage to care, and the initiation of treatment when the client is ready, has the potential to greatly reduce HIV transmission.
Early identification of HIV infection also benefits the individual. People who know they live with HIV can seek care and treatment, and early treatment can improve their health and well-being. People living with HIV who begin treatment shortly after diagnosis and take the required medicines every day are expected to live a near-normal lifespan.5 Benefits of care can also include receiving an array of medical and social services such as preventative treatment (prophylaxis) for opportunistic infections, treatment for sexually transmitted infections (STIs), treatment for substance use and mental health conditions, as well as access to income supports and housing.
Approaches to HIV Contact Tracing
The Canadian Guidelines on Sexually Transmitted Infections provide recommendations for contact tracing. According to these guidelines, partner notification may be done by the patient, healthcare provider or public health authority, or a combination of more than one may be used to notify different partners of the same person.
Of the 13 other jurisdictions in Canada, 11 have public health laws that cover contact tracing. These can be divided into two groups: British Columbia, Saskatchewan, Manitoba, Prince Edward Island, Nunavut and Northwest Territories require contact tracing to be performed when someone is diagnosed with HIV. In comparison, Alberta, Ontario, New Brunswick, Nova Scotia and Yukon allow contact tracing to occur.6 The remaining two jurisdictions (Quebec, Newfoundland and Labrador) have no specific laws mandating contact tracing, but health officials conduct contact tracing based on available guidelines.6
Whether healthcare providers and public health staff follow contact tracing guidelines with every client may be impossible to know. British Columbia has begun tracking whether public health has followed up with newly diagnosed patients. About 70% of these patients in 2013 had a record of public health follow-up.7 In the United States, there is some evidence that follow-up rates are much lower.8
There are three main contact tracing methods used in Canada:
Patient-referral contact tracing is when a person newly diagnosed with HIV tells (notifies) their sexual and drug-using partners that they may have been exposed to HIV. Typically, the person, sometimes called the index patient, is helped by their healthcare provider or public health staff to figure out who should be told and how to tell them.
Provider-referral contact tracing is when a healthcare provider or someone from public health notifies the index patient's sexual or drug-using partners that they may have been exposed to HIV.
Contact tracing is also sometimes done through contract referral programs. This is a hybrid method where the individual tells some of their contacts and their healthcare provider or public health staff tells others. In some instances, if a patient has not told their partners within an agreed-upon timeframe, their healthcare providers or public health staff will complete notification for them.
Depending on which method of contact tracing is used, there are typically ways for the index patient's anonymity to be preserved when disclosure is made to potential contacts.
Challenges to Effective Contact Tracing
One of the obstacles to effective contract tracing is the willingness of providers to do contact tracing or to refer clients to public health for contact tracing. Although most providers are in favour of contact tracing,9 studies have shown that providers are inconsistent in offering it. In one American city, as many as 48% of index patients were not referred for contact tracing.8 Even when a person newly diagnosed with HIV shares their contacts with a healthcare provider or public health nurse, there is no guarantee that their contacts will be notified. One study from the United States estimated that only 32% of notifiable partners were reached when contacts were shared.10
The second obstacle to effective contact tracing is the ability to locate and inform contacts. Increasingly this is becoming a problem with the introduction of new technologies, which connect people to new sexual partners, often anonymously. In a study out of the United States, 12% of gay and other men who have sex with men (MSM) and heterosexuals could not share their contacts' information because they did not know their sexual partners' names.11
The Acceptability of Contact Tracing: Patient and Provider Referral
Patient-referral contact tracing is acceptable to clients.12-14 The acceptability of patient-referral contact tracing ranges from 55% to 97% when clients are asked if they would, hypothetically, be willing to personally disclose to partners if they were diagnosed with HIV.9
However, when people recently diagnosed with HIV are asked whether they prefer to notify their partners personally or to have a healthcare provider or public health professional do it for them, more people choose to have their providers notify their contacts than choose to tell their partners themselves.9
Overall, patient-referral contact tracing tends to work better than provider-referral contact tracing when index patients have had unprotected sex, when individuals know how to find their sexual partners, and when they do not have any casual sex partners.15
Provider-referral contact tracing is also acceptable to clients. Acceptability varies depending on sexual orientation,9 gender,9 drug-using behaviours,9 and what type of healthcare provider (public health professional or physician) would be notifying partners of their potential exposure.16 Acceptability ranges from 80% among MSM to 92% among heterosexual men.9
Is Contact Tracing Effective?
Contact tracing seems to be effective at getting people to test for HIV and finding new HIV cases. A systematic review found that 63% of notified partners were tested for HIV.17 The same systematic review also showed that the average percentage of people of those contacted who tested positive was 20%, with a range of 14% to 26%.17
Contact tracing is also effective at getting untested people into testing. In one study, 22% of people who tested as a result of contract tracing had never had a test before and 41% had no plans to be tested within the next 6 months.11
Contact tracing is effective at reducing risky behaviours. An American study found a reduction in the usual needle-sharing behaviour and number of sex partners in people who were notified and tested for HIV. When a notified person was diagnosed with HIV, an 80% reduction in risk behaviours at 6 months was shown.18 When the notified person tested negative for HIV, there was a 50% reduction in risk behaviours.18
Finally, contact tracing appears to be cost-effective. Cost-effectiveness of contact tracing can be measured in two ways: how much does it cost to prevent a new infection or how much does it cost to find a new infection?
In the United States in 2004, it was estimated that the lifetime direct cost of medical care for someone living with HIV was about US$385,000.19 It has also been estimated that HIV contact tracing costs US$6,100 to prevent a new infection, which is significantly less than the cost of providing medical care to someone living with HIV.19
It has been estimated that if the cost of finding a new HIV infection is below US$30,000, then it would be cost-effective.20 A study in San Francisco found that it cost about US$7,081 to find a new infection,21 well below this estimated cost, making it a cost-effective intervention. However, it should be noted that these studies are almost 10 years old and new studies are needed to update these numbers.
This article was provided by Canadian AIDS Treatment Information Exchange. It is a part of the publication Prevention in Focus: Spotlight on Programming and Research. Visit CATIE's Web site to find out more about their activities, publications and services.
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