Imperial College London


Faculty of MedicineSchool of Public Health

Senior Lecturer



+44 (0)20 7594 1933e.volz Website




UG10Norfolk PlaceSt Mary's Campus






BibTex format

author = {Romero-Severson, EO and Volz, E and Koopman, JS and Leitner, T and Ionides, EL},
doi = {aje/kwv044},
journal = {American Journal of Epidemiology},
pages = {255--262},
title = {Dynamic Variation in Sexual Contact Rates in a Cohort of HIV-Negative Gay Men},
url = {},
volume = {182},
year = {2015}

RIS format (EndNote, RefMan)

AB - Human immunodeficiency virus (HIV) transmission models that include variability in sexual behavior over timehave shown increased incidence, prevalence, and acute-state transmission rates for a given population risk profile.This raises the question of whether dynamic variation in individual sexual behavior is a real phenomenon that can beobserved and measured. To study this dynamic variation, we developed a model incorporating heterogeneity inboth between-person and within-person sexual contact patterns. Using novel methodology that we call iterated filteringfor longitudinal data, we fitted this model by maximum likelihood to longitudinal survey data from the Centersfor Disease Control and Prevention’s Collaborative HIV Seroincidence Study (1992–1995). We found evidence forindividual heterogeneity in sexual behavior over time. We simulated an epidemic process and found that inclusion ofempirically measured levels of dynamic variation in individual-level sexual behavior brought the theoretical predictionsof HIV incidence into closer alignment with reality given the measured per-act probabilities of transmission.The methods developed here provide a framework for quantifying variation in sexual behaviors that helps in understandingthe HIV epidemic among gay men.
AU - Romero-Severson,EO
AU - Volz,E
AU - Koopman,JS
AU - Leitner,T
AU - Ionides,EL
DO - aje/kwv044
EP - 262
PY - 2015///
SN - 0002-9262
SP - 255
TI - Dynamic Variation in Sexual Contact Rates in a Cohort of HIV-Negative Gay Men
T2 - American Journal of Epidemiology
UR -
UR -
VL - 182
ER -