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CDC Says New HIV Transmissions Stem From Lack of Treatment, Unawareness of Infection


The majority of new HIV infections have been found to be transmitted by individuals who are unaware that they have HIV or by those who know they have HIV but are not receiving treatment to suppress their infection.

Nearly 80% of new HIV infections are transmitted by individuals who are unaware that they have HIV or by those who know they have HIV but are not receiving treatment, according to the CDC’s Morbidity and Mortality Weekly Report.

Greater occurrence of viral suppression must be achieved in individuals with HIV to prevent transmission of the disease and end the epidemic in the United States, the CDC said. HIV treatment has recently become more manageable and effective.

“Today’s treatment regimens are simpler than those prescribed in the past, sometimes requiring only single-tablet formulations, with fewer side effects; most persons with HIV infection can achieve viral suppression within 6 months of initiating treatment,” the report said. The spread of HIV can be prevented by awareness of HIV infection status, behavior changes, and by consistent antiretroviral therapy (ART). Individuals who achieve and retain viral suppression have been found to pose practically no risk of transmission to their sexual partners.

The CDC used the Progression and Transmission of HIV 2.0 (PATH 2.0) model to estimate national transmission rates, using data from 2016. The total estimated population of individuals living with HIV was 1.1 million people, and the number of new transmissions that year was estimated to be 38,700.

It was found that the majority of HIV was transmitted by individuals who were unaware they had the disease or by those who knew they had HIV but were not receiving treatment. Together, these groups accounted for approximately 80% of new infections. Individuals who were receiving care but had not reached viral suppression accounted for nearly 20% of transmissions.

Data on estimated prevalence and incidence of HIV, records of care, and viral suppression were obtained from National HIV Surveillance System. Instances of transmission were attributed to groups of individuals separated by awareness and severity of their infection, whether they received care or treatment, and whether they have achieved viral suppression. Percentages of transmissions generated by each group were:

  • 4% from acutely infected individuals unaware of their infection
  • 33.6% from non-acutely infected individuals unaware of their infection
  • 42.6% from individuals aware of their HIV infection but were not receiving care
  • 19.8% from individuals receiving care but were not virally suppressed
  • 0% from individuals taking ART who were virally suppressed

The total estimated rate of HIV transmission in 2016 was 3.5 new infections per 100 person-years. Rates by person-years, from greatest to least were:

  • 16.1 by individuals acutely infected and unaware they had HIV
  • 8.4 by individuals non-acutely infected and unaware they had HIV
  • 6.6 by individuals aware of their HIV infection but were not seeking care
  • 6.1 by individuals receiving care but not virally suppressed
  • 0 by individuals taking ART who were virally suppressed

Information on sexual and needle-sharing behaviors was obtained from National HIV Behavioral Surveillance System. In evaluating HIV transmissions among mutually exclusive population risk groups, it was found that:

  • 73% from men who have sex with men (MSM)
  • 7.2% from men who inject drugs
  • 2.6% from women who inject drugs
  • 5.3% from MSM who inject drugs
  • 6.1% from heterosexual men
  • 5.8% from heterosexual women

Rates of transmission were found to decrease as individuals received treatment for longer periods of time. However, barriers to care include lack of health insurance, housing issues, stigma and discrimination, lack of transportation, mental health and substance use problems, and lack of trust in the medical system.

“Although the prevalence of viral suppression among persons with HIV infection has been increasing, and the number of new infections and transmission rates have been decreasing in the United States, faster rates of change are needed to end the HIV epidemic in the United States. To accelerate progress, persons with HIV infection must receive a diagnosis soon after infection, begin treatment rapidly after diagnosis, adhere to treatment, and receive support services that help achieve and sustain viral suppression,” the report said.


Zihao L, Purcell DW, Sansom SL, Hayes D, Hall HI. Vital Signs: HIV transmission along the continuum of care — United States, 2016 [published online March 18, 2019]. MMWR Morb Mortal Wkly Rep. doi: 10.15585/mmwr.mm6811e1.

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