Index Testing for HIV: Finding Infections Among Contacts in 20 Countries, 2016–2018

In 2017, UNAIDS estimated that 36.9 million people worldwide were living with HIV, and about 75% knew it — leaving 9.4 million undiagnosed. UNAIDS aimed for 90% to know their status by 2020; population surveys in 10 African countries found that, as of 2018, the share ranged from 37% in Côte d'Ivoire to 86% in Namibia.

Index testing — also called partner notification or contact tracing — targets people most likely to be infected. HIV-positive "index" patients voluntarily name their sexual and needle-sharing partners and biological children; the patient or a provider contacts them, and those who don't know their status are offered testing. Studies show it is effective and cost-effective.

The program

Since 2003, the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) has provided about $72 billion for HIV testing and treatment in 37 countries and regions; in 2017 alone it supported 85.5 million rapid HIV tests and linked 14 million people to antiretroviral treatment. Index testing became a reporting category in October 2016.

This report covers October 1, 2016 – March 31, 2018 in 20 CDC-supported countries: Botswana, Cameroon, Côte d'Ivoire, the Democratic Republic of the Congo, Eswatini, Ethiopia, Haiti, Kenya, Lesotho, Malawi, Mozambique, Namibia, Rwanda, South Africa, South Sudan, Tanzania, Uganda, Vietnam, Zambia and Zimbabwe.

Findings

• Kenya, Mozambique and Tanzania accounted for more than half of all tests and positives.
• Growth: quarterly tests rose from 166,108 to 356,573, and positives more than tripled, from 8,186 to 27,893. Positivity climbed from 4.9% to 7.8% overall — from 7.6% to 12.5% (up 64%) among those 15 and older, and 1.2% to 2.0% (up 67%) among children under 15.
• By sex and age (15+ with sex reported, 865,126 people): 55% women, 45% men. Positivity was lowest at ages 10–14 (1.1% boys, 1.3% girls) and highest at 25–49 (13.0% men, 13.5% women); overall 7.5% for women and 6.8% for men.

HIV tests and positivity through index testing, by fiscal quarter. CDC.

Why it matters

Across all testing approaches, PEPFAR partners in these countries gave 66 million tests, with positivity of 1.0% under 15 and 4.1% at 15 and older. Index testing found infections at more than twice that rate — while making up only 2.4% of all tests. It is likely most productive where HIV service coverage is low, and it reaches men, who other approaches may miss. Children usually acquire HIV at birth, which is why their positivity is far lower than adults', who are infected by sexual and needle-sharing partners.

Scaling up index testing could help more people learn their status, start treatment, and so stop transmitting the virus.

Limitations: the data may count people tested more than once — routine data are aggregated and many countries lack unique identifiers; countries were at different stages of adopting index testing (the WHO issued partner-notification guidelines only in December 2016), and partners may have misclassified contacts such as neighbors; and ages 25–49 were reported as one group (PEPFAR asked for 5-year groups from October 2018).

Sources

Based on Lasry A, Medley A, Behel S, et al., "Scaling Up Testing for Human Immunodeficiency Virus Infection Among Contacts of Index Patients — 20 Countries, 2016–2018," MMWR Morbidity and Mortality Weekly Report, volume 68, Centers for Disease Control and Prevention; a work of the United States government in the public domain.