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Detecting highly transmissible acute HIV
CDC: NY success may lead to national effort
Screening STD clinic patients — especially men who have sex with men (MSM) — for signs of an acute, highly transmissable stage of HIV infection could heighten detection and prevention efforts, the Centers for Disease Control and Prevention. "Surveillance for acute human immunodeficiency virus (AHI) is feasible and can identify circumstances in which HIV prevention efforts should be intensified," the CDC emphasized in a recently published report.1 CDC is considering a national AHI case definition for use in national HIV surveillance to identify areas or populations in which HIV infection is spreading, and for assessing new methods for AHI screening.
(AHI) is a highly infectious phase of disease that lasts approximately two months and is characterized by nonspecific clinical symptoms. AHI contributes disproportionately to HIV transmission because it is associated with a high level of viremia, despite negative or indeterminate antibody (Ab) tests. Diagnosis of AHI with individual or pooled nucleic acid amplification tests (p-NAAT) can enable infected persons to adopt behaviors that reduce HIV transmission, facilitate partner referral for counseling and testing, and identify social networks of persons with elevated rates of HIV transmission. Unfortunately, the national HIV surveillance case definition does not distinguish AHI from other stages of HIV infection, and the frequency of AHI among reported HIV cases is unknown.
In 2008, to increase detection of AHI and demonstrate the feasibility of AHI surveillance, the New York City Department of Health and Mental Hygiene (NYC DOHMH) initiated p-NAAT screening at four sexually transmitted disease (STD) clinics and enhanced citywide HIV surveillance (using a standard case definition) to differentiate AHI among newly reported cases. Seventy cases of AHI (representing 1.9% of all 3,635 HIV diagnoses reported in New York City) were identified: 53 cases from enhanced surveillance and 17 cases from p-NAAT screening (representing 9% of 198 HIV diagnoses at the four clinics). Men who have sex with men (MSM) constituted 81% of AHI cases.
"The findings in this report confirm that p-NAAT can increase AHI diagnoses among high-risk STD clinic patients, and indicate that AHI diagnoses can be made apart from p-NAAT screening programs," the CDC concluded.
The 70 AHI cases identified by NYC DOHMH represent a fraction of the 4,762 new infections previously estimated to occur annually in New York City, highlighting the need to improve awareness and detection of AHI. Notably, 81% of AHI cases identified in New York City were among MSM, reflecting the high HIV incidence in MSM and demonstrating the risk for missed diagnoses when HIV-Ab testing alone is used in a high-risk, high-incidence population. Without p-NAAT screening, 9% of the HIV infections documented by the four STD clinics during the screening period would have been missed. However, because HIV RNA is not detectable for approximately 10 days after infection), even NAAT will not identify all infected persons. The CDC recommends that persons with very recent high-risk exposures be encouraged to retest after 4 to 6 weeks, even if p-NAAT is negative. Based on the results, NYC DOHMH has expanded p-NAAT screening to all nine New York City STD clinics and improved ascertainment of AHI in routine surveillance.