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Transmission dynamics among participants initiating antiretroviral therapy upon diagnosis of early acute HIV-1 infection in Thailand

Kroon, Eugènea,b; Pham, Phuc T.c,d; Sirivichayakul, Suneee; Trichavaroj, Rapeef; Colby, Donn J.a,b; Pinyakorn, Suteeraporna,c,d; Phanuphak, Nittayaa,b; Sanders-Buell, Ericc,d; van Griensven, Fritsb,g; Kijak, Gustavo H.c,d; Kim, Jerome H.c,d,f,i; Michael, Nelson L.c,h; Robb, Merlin L.c,d; Ananworanich, Jintanata,c,d; De Souza, Mark S.a,b,d; Tovanabutra, Sodsaic,d on behalf of the RV254/SEARCH 010 Study Group

doi: 10.1097/QAD.0000000000001956
Epidemiology and Social

Objective: To assess transmission characteristics in a predominantly MSM cohort initiating antiretroviral therapy (ART) immediately following diagnosis of acute HIV-1infection (AHI).

Methods: A longitudinal study (2009–2017) was performed in participants with AHI (n = 439) attending a single clinic in Bangkok. Plasma samples obtained prior to ART were used to obtain HIV-1 pol sequences and combined with clinical and epidemiologic data to assess transmission dynamics (cluster formation and size) using phylogenetic analysis. Clusters were estimated using maximum likelihood, genetic distance of 1.5% and visual inspection. The potential transmitter(s) in a cluster was determined using time to viral suppression and interview data.

Results: The cohort was predominantly MSM (93%) and infected with HIV-1 CRF01_AE (87%). Medians (ranges) for age and viral load prior to ART were 26 (18–70) years and 5.9 (2.5–8.2) log10 HIV-1 RNA copies/ml. Median time from history of HIV-1 exposure to diagnosis was 19 (3–61) days. Viral suppression was observed in 388 of 412 (94%) participants at a median time of 12 weeks following ART. Twenty-six clusters with median cluster size of 2 (2–5) representing 62 of 439 (14%) participants were observed. Younger age was associated with cluster formation: median 28 versus 30 years for unique infections (P = 0.01). A potential transmitter was identified in 11 of 26 (42%) clusters.

Conclusion: Despite high rates of viral suppression following diagnosis and treatment of AHI within a cohort of young Thai MSM, HIV-1 transmission continued, reflecting the need to expand awareness and treatment access to the entire MSM population.


bThe Thai Red Cross AIDS Research Centre, Bangkok, Thailand

cUnited States Military HIV Research Program, Bethesda

dThe Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, Maryland, USA

eDepartment of Medicine, Faculty of Medicine, Chulalongkorn University

fDepartment of Retrovirology, Armed Forces Research Institute of Medical Sciences, United States Component, Bangkok, Thailand

gDepartment of Preventive Medicine and Public Health, University of California at San Francisco, San Francisco, California

hWalter Reed Army Institute of Research, Silver Spring, Maryland, USA

iInternational Vaccine Institute, Seoul, Korea.

Correspondence to Eugène Kroon, MD, Thai Red Cross AIDS Research Centre, 104 Ratchdamri Road, Pathumwan, Bangkok 10330, Thailand. Tel: +66 2 254 2566; fax: +66 2 254 2567; e-mail:

Received 20 October, 2017

Revised 16 June, 2018

Accepted 22 June, 2018

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