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Acute-Stage Transmission of HIV: Effect of Volatile Contact Rates

Romero-Severson, Ethan Obie; Alam, Shah Jamal; Volz, Erik; Koopman, James

doi: 10.1097/EDE.0b013e318294802e
Infectious Diseases

Background: The role of acute-stage transmission in sustaining HIV epidemics has been difficult to determine. This difficulty is exacerbated by a lack of theoretical understanding of how partnership dynamics and sexual behavior interact to affect acute-stage transmission. We propose that individual-level variation in rates of sexual contact is a key aspect of partnership dynamics that can greatly increase acute-stage HIV transmission.

Methods: Using an individual-based stochastic framework, we simulated a model of HIV transmission that includes individual-level changes in contact rates. We report both population-level statistics (such as prevalence and acute-stage transmission rates) and individual-level statistics (such as the contact rate at the time of infection).

Results: Volatility increases both the prevalence of HIV and the proportion of new cases from acute-stage infectors. These effects result from 1) a relative reduction in transmission rate from chronic but not acute infectors and 2) an increase in the availability of high-risk susceptibles.

Conclusions: The extent of changes in individual-level contact rates in the real world is unknown. Aggregate or strictly cross-sectional data do not reveal individual-level changes in partnership dynamics and sexual behavior. The strong effects presented in this article motivate both continued theoretical exploration of volatility in sexual behavior and collection of longitudinal individual-level data to inform more realistic models.

From the Department of Epidemiology, University of Michigan, Ann Arbor, MI.

Supported by NIH R01-AI078752. E.V. was also supported by NIH 1-K01-AI-091440-01.

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Correspondence: Ethan Obie Romero-Severson, Department of Epidemiology, University of Michigan, 335 E Kingsley #2, Ann Arbor, MI 48104. E-mail:

Received November 14, 2011

Accepted January 31, 2013

© 2013 by Lippincott Williams & Wilkins, Inc