Using physician visits for a GH diagnosis as proxies, the present study explored the annual numbers and rates of diagnosed cases of GH in Canada from 2002 to 2007. Physician visits depended on several factors such as severity of infection, individual awareness of signs and symptoms of infection, individual testing behaviour and access to health care services and, as such, do underestimate the burden of infection. The present study found that the number of medically attended GH cases in Canada in a year ranged from 84,398 to 122,456, translating to a rate of between 261.2 and 386.6 per 100,000 population. That is, at any given time, between 0.3% to 0.4% of the general population in Canada might be seeking treatment for GH. However, this is likely an underestimate of the true burden of this infection because atypical and subclinical infections often go unrecognised or undiagnosed. Fleming et al (19
) found that only approximately 9.2% of all those who were HSV-2-seropositive reported a known history of GH. It has been reported that more than 60% of HSV-2-seropositive persons experience symptoms, but do not associate them with genital HSV infection, approximately 20% remain asymptomatic and less than 20% receive a diagnosis of GH (20
). Studies further suggest that asymptomatic infected patients can contribute to the transmission of GH (21
The present analysis suggests that between 6.8% and 25.9% of the diagnosed cases consulted a physician more than once, with a range of two to eight visits per year. This is consistent with previous research, which also suggests that GH may reoccur from zero to six or more times a year (22
). Generally, all cases of recurrent GH are due to reactivation of a latent infection rather than to reinfection (23
). Genital HSV-1 reoccurs less frequently than genital HSV-2, and its rate decreases further over time (24
). Recurrent GH is frequent in the first year in more than 80% to 90% of individuals following primary genital HSV-2 infection, compared with less than 50% to 55% of individuals following primary genital HSV-1 infecton (25
). Data according to viral subtype or the category of infection were not available in the present study. Further study is needed to differentiate between primary and recurrent GH infections, (ie, incident and prevalent cases); this could be accomplished through further data mining of CDTI for data for any drug recommended in the prescription diary, because the dosage of antivirals in initial infection is different from the suppressive therapy for recurrent infections.
A comparison with reportable STIs in Canada reveal that there were 73,770 genital chlamydia cases, 11,873 gonorrhea cases and 1206 infectious syphilis cases reported in 2007, versus 118,044 medically attended GH cases in 2007 and an estimated 41,450 incident cases of anogenital warts in 2006 (26
The present study is the first time that administrative data have been used to estimate the rate of medically attended GH in Canada – a preliminary first estimate, notwithstanding data limitations. The present study estimated an annual rate of between 261.2 and 386.6 medically attended GH cases per 100,000 population in Canada for the period between 2002 and 2007, compared with a rate of between 32.5 and 42.7 new diagnoses of GH (at genitourinary medicine clinics) per 100,000 population in the United Kingdom for the period of 2005 to 2007 (29
). An extrapolation of the data from CDTI found that there were 84,398 to 122,456 medically attended GH cases in Canada between 2002 and 2007, compared with between 203,000 and 317,000 initial physician visits for GH reported by the National Disease and Therapeutic Index of the United States for the same period (30
The present study is not free of limitations. The source database (CDTI) assesses diagnosis volume in office-based practice (physicians); STI clinics, nurse practitioners or other health care providers are not included. The sample size is small and carries the risk of attrition of sentinel practices or selection bias. Granular data were not available for the persent study according to viral subtype, demography (sex, age, ethnicity, location), category of infection (primary, recurrent, nonprimary first episode), diagnostic criteria, or symptom duration and outbreak frequency. The database is unable to directly differentiate between initial or primary and recurrent genital HSV infections, or to differentiate prevalence from incidence rates. Also, the CDTI is unable to inform on the estimated annual health care costs for the GH cases reported.
In view of the atypical, subclinical or unrecognized manifestations of GH, there is often a delay between occurrence of initial symptoms and a patient’s visit to a physician and subsequent diagnosis. Typical herpetic lesions may be recognizable during clinical examination, but require confirmation through viral identification techniques such as viral culture, nucleic acid amplification techniques or type-specific serology.