People with a low detectable viral load are at risk for serious non-AIDS-defining events, such as cancer, heart disease and liver or kidney disease. Maintaining an undetectable viral load can halt progression of HIV and eliminate the risk of transmission. Many viral load tests measure down to 50 copies of HIV RNA—the usual threshold for undetectable—but some experts still regard levels below 200 or even 1,000 as viral suppression. In an analysis of nearly 3,000 people who started HIV treatment after 1996, 8% had a low-level detectable viral load (50 to 200 copies), 4% had 200 to 1,000 copies and a third experienced virological failure. Over 10 years, nearly 14% experienced serious non-AIDS events. People with a viral load between 50 and 200 were 25% more likely to do so than those with full viral suppression. What’s more, people who waited longer to start antiretroviral therapy and those who had a higher viral load or a lower CD4 count at treatment initiation were at greater risk even if they later achieved viral suppression and T-cell recovery.