HIV prevention continues to be a public health priority in British Columbia (BC). Incidence and prevalence are two measures of disease frequency used to inform our response to the HIV epidemic. Incidence is the number of new infections (both diagnosed and undiagnosed) that occur in an area over a year whereas prevalence is the total number of people living with HIV in that area in that year.
Routine surveillance of HIV is based on new diagnoses of HIV [BC HIV Annual Report 2017]. However, because people can be living with HIV for a long time before they are diagnosed, the number of new HIV diagnoses is only an approximation of HIV incidence. Similarly, accurate prevalence estimates need to account for people living with HIV who are not yet diagnosed, migration (i.e., people living with HIV who move into or out of BC) and death which are not available through routine surveillance. For these reasons, mathematical models are needed to incorporate various sources of knowledge about the HIV epidemic to better estimate HIV incidence and prevalence in a population.
The Public Health Agency of Canada (PHAC) has released national estimates of HIV incidence and prevalence for 2018 based on multiple data sources, including routine HIV surveillance data [Canadian estimates]. Below is a summary of PHAC’s estimates for HIV incidence and prevalence for BC in 2016 and 2018.
Note the 2016 estimates presented below differ from those that were previously published [SmartSexResource]. This is because the methodology for calculating HIV incidence and prevalence has been revised to incorporate additional data sources and also the updating of HIV surveillance data due to late reporting. The revised methodology has been applied to generate both the 2016 and 2018 estimates presented below.
1) The number of new HIV infections (incidence) has decreased from 2016 to 2018
Overall, the incidence of HIV has been decreasing in BC since the mid 1980s (Figure 1).
Figure 1: Estimated number of incident HIV infections in British Columbia, 1975 to 2018
In BC, estimates of the total number of incident or new HIV infections in 2018 was 165 (range 80-280), a decrease from 188 (range 110-265) in 2016 (Table 1). In 2018, incident HIV infections continued to be higher among males than females.
Gay, bisexual, or other men who have sex with men (gbMSM) continued to comprise the greatest number of new HIV infections (106 infections; 64%) followed by people who acquired HIV through heterosexual contact (37 infections; 22%). The number of new HIV infections among people who inject drugs (PWID) increased slightly to19 infections (12%) in 2018 from 14 infections (7%) in 2016.
Table 1: Estimated number of incident HIV infections in British Columbia, 2016 and 2018
2) The number of people living with HIV infection (prevalence) has remained stable from 2016 to 2018
The estimate of prevalent HIV infections or the total number of people living with HIV in BC at the end of 2018 was 9,836 (range 8,560-11,200), similar to 9,875 (range 8,690-11,180) at the end of 2016 (Table 2). In 2018, prevalent HIV infections continued to be higher among males than females which likely reflect the distribution of incident HIV infections between males and females in BC.
Among people living with HIV in 2018, gbMSM continued to comprise the greatest proportion of prevalent infections (5,020 infections; range 4,360-5,700), followed by heterosexual persons (2,460 infections; range 2,140-2,800) then PWID (1,960 infections; range 1,700-2,230).
Table 2: Estimated number of prevalent HIV infections in British Columbia, 2016 and 2018
PHAC HIV estimates compared to routine HIV surveillance in BC
Overall, the estimates of HIV incidence released by PHAC are consistent with the BC Centre for Disease Control’s (BCCDC) HIV surveillance data which show a decreasing trend in the number of new HIV diagnoses and, gbMSM continuing to comprise the greatest number of new HIV diagnoses in BC. Stable HIV prevalence may reflect the lower number of new HIV diagnoses each year and a low mortality rate due to improved prevention of and treatment for HIV.
These estimates of HIV incidence and prevalence along with routine HIV surveillance data are essential to monitor the HIV epidemic and to measure the progress towards ensuring people living with HIV are aware of their diagnoses and engaged in care. This includes addressing HIV-related stigma and improving access to prevention, testing, and treatment services that are both culturally safe and appropriate.
National estimates are presented in more detail in Estimates of HIV incidence, prevalence and Canada’s progress on meeting the 90-90-90 HIV targets on the Government of Canada website.
Provincial HIV surveillance data are shown in the HIV/AIDS Reports section on the BCCDC website.
Previously published provincial estimates for 2014 and 2016 are described in the blog HIV incidence and prevalence estimates for British Columbia and Canada in 2016 on the SmartSexResource website.
Public Health Agency of Canada (PHAC)