CDC Model Identifies Those at Greatest Risk of Transmitting HIV

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2 min readSep 29, 2020


Model divides individuals into 5 categories

Summary by Dr. Kenneth Fife

Scientists at the US Centers for Disease Control and Prevention (CDC) have developed a model that identifies individuals at greatest risk of transmitting HIV, and helps to design strategies to reduce (and eventually eliminate) HIV transmission in the US.

Individuals infected with HIV were divided into 5 categories:

1) recently infected (> 3 months) and unaware of their infection status

2) chronically infected (>3 months) and unaware of their status

3) chronically infected and aware of their status, but not receiving care

4) chronically infected, in care, with detectable viral loads

5) chronically infected, in care, with undetectable viral loads

Group 1 had the highest rate of transmission. With the highest viral load, group one’s risk of transmission was twice that of group two. However, the period of high infectivity was limited, accounting for only 4% of HIV transmissions. Group 2 (chronic infection, unaware of status) had the second highest rate of communication, accounting for about a third (33.6%) of transmissions. Those who knew their status but were not receiving care, group 3, had a transmission risk similar to group 2, but they accounted for just under half (42%) of all transmissions. Group 4 (in care but not suppressed) had a similar transmission rate and accounted for about one-fifth (19.8%) of transmissions. Those in treatment and fully suppressed, group 5, had a transmission rate of 0 and accounted for no transmissions.

Groups 1, 2, and 3 account for roughly 80% of HIV transmission, and should be the initial targets of intervention. The CDC recommends that every American between the ages of 13 and 64 be tested for HIV at least once in their lifetime, regardless of risk behavior. They also recommend that people with ongoing risk of HIV transmission be tested once, or more, per year, for as long as they remain at risk.

Equally important is the need to link patients who’ve tested positive for HIV to comprehensive care. In comprehensive care programs, most people can get their viral loads to undetectable levels within a few weeks, or months, of starting treatment. The goal for US care should align with the global HIV target, 90–90–90.

That is, 90% of the population screened for HIV, 90% of HIV positive people referred for treatment, and 90% of those in treatment achieving undetectable viral loads. Accomplishing these goals will go a long way toward stopping the transmission of HIV.



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