Case reports are the basis of most sexually-transmitted infection (STI) reporting systems, but reliance on case data alone is limited by an inability to describe trends among key populations, such as gay, bisexual and other men who have sex with men (MSM).
Sentinel surveillance, in which disease monitoring is done at select sites when population-level estimates are not available, is one approach to overcome this limitation.
We developed a sentinel surveillance system with data from public health STI clinics that use a common electronic medical record system. We included MSM clients who visited these STI clinics throughout British Columbia (BC) from 2000-2013.
Diagnosis rates were estimated for Chlamydia, gonorrhea, syphilis, HIV, hepatitis C, genital herpes, and genital warts. The diagnosis rate was calculated by dividing the number of unique cases by the number of unique clients who tested for the STI each year.
Data for HIV were included starting in 2004, a year after HIV became a notifiable communicable disease in BC.
The overall diagnosis rates were highest for Chlamydia and gonorrhea. While trends for most STI were stable, diagnoses of gonorrhea and syphilis among MSM have risen steadily in recent years. Diagnoses of new HIV cases have remained constant over time, while rates of genital herpes and warts have also remained steady. There was a pronounced decline in diagnosis of hepatitis C during the period 2000-2004, and this drop has been sustained in subsequent years (Figure 1).
In another finding, HIV co-infection was associated with higher gonorrhea and syphilis rates. Further investigation is required to explore the syndemic effects of syphilis, gonorrhea and HIV that may be contributing to ongoing transmission among MSM. The increase in gonorrhea and syphilis cases could reflect different sexual networks involving HIV-positive men or different routes of transmission (e.g., oral sex).
Figure 1: Diagnosis rates among MSM for each STI per 1000 persons, 2000-2013. Dashed lines represent the 95% confidence intervals.
We have described STI trends among MSM in BC using a sentinel site surveillance approach. This is the first report of STI trends among MSM from a network of sentinel STI clinics in Canada.
Our new platform will be a valuable tool for ongoing monitoring of STI and for targeting prevention efforts to reduce the burden of disease in the province.
For further information
Ling DI, Janjua NZ, Wong S, Krajden M, Hoang L, Morshed M, Achen M, Murti M, Lester RT, Wong J, Ogilvie G, Gilbert M. Sexually transmitted infection trends among gay or bisexual men from a clinic-based sentinel surveillance system in British Columbia, Canada. Sex Transm Dis. 2015 Mar;42(3):153-9.
Link to PubMed abstract: http://www.ncbi.nlm.nih.gov/pubmed/25668648
Jason Wong, Naveed Janjua, Stanley Wong, Mel Krajden, Linda Hoang, Muhammad Morshed, Melanie Achen, Michelle Murti, Richard Lester, Gina Ogilvie, Mark Gilbert