Background:  Increasing risk behaviour and resurgent HIV epidemics have been widely reported among men who have sex with men (MSM) in the era of combination ART (cART). We analyzed the effect of cART on the transmission dynamics of HIV-1 among patients in the Netherlands infected via heterosexual contact.

Methods:  Heterosexually infected patients diagnosed until 2007 were selected from the ATHENA national observational cohort and classified according to their region of infection (Netherlands, other Western countries, Sub-Saharan Africa, other countries). HIV-1 subtypes were determined from protease and RT sequences, obtained during routine clinical care. A mathematical model was used to estimate changes in transmission and diagnosis rates, and immigration patterns needed to explain the observed data on HIV and AIDS diagnoses and the transmission of non-B subtypes in the Netherlands. The reproduction number R(t), the average number of individuals infected by each HIV-infected patient during his infectious lifespan, was calculated in three distinct periods. Sensitivity analyses were performed to assess the dependence on model assumptions.

Results:  We selected 4676 patients, of whom 1966 (42.0%) were infected in the Netherlands, 186 (4.0%) in other Western countries, 1921 (41.1%) in Sub-Saharan Africa, and 603 (12.9%) in other regions. Of 1344 (28.7%) patients with a known HIV-1 subtype, 802 (59.7%) were infected with a non-B subtype. The annual number of diagnoses increased from 139 in 1996 to 433 in 2006 and was 324 in 2007. According to the model, the average time from infection to diagnosis in 1984 to 1995, 1996 to 2000, and after 2000 was 3.7, 3.7, and 3.0 years, respectively. Compared to 1984 to 1995, transmission rates were 16% (range of sensitivity analyses, 1 to 18) lower in 1996 to 2000, and R(t) decreased from 1.37 (0.99 to 1.44) to 0.87 (0.65 to 1.00). After 2000, transmission rates increased by 29% (5 to 37), or 9% (6 to 21) compared to 1984-1995, resulting in an increase of R(t) to 1.06 (0.85 to 1.10). The estimated annual number of new infections increased from 92 in 2000 to 235 in 2007.

Conclusions:  Our model indicates that transmission rates in the heterosexual population in the Netherlands have increased in recent years. Though these increases are less marked than in the MSM population, the current reproduction number is near or above the epidemic threshold, and the local HIV epidemic of subtype B virus among heterosexuals appears to be self-sustaining.