Infectious diseases surveillance among injection drug users - Epidemiology of HIV from 1995 to 2004 - Epidemiology of HCV from 2003 to 2004

As of June 30, 2004, 14,773 questionnaires had been administered to 8,964 individuals (Table 1).

Three-quarters of participants are men (6,542/8,964) with an average age of 33. The average age of female participants is 28 (Table 1).

Educational levels are low, with only one in four (269/1,105) participants having completed high school (Table 3; 2003-04 data).

Cocaine is the injection drug most often used (88% of the 8,939 respondents had used cocaine), followed by heroin at 36% (Table 5). Cocaine is also the drug most frequently injected by 75% (6,639/8,897) of participants (Table 9).

Injection drug use varies a lot by region (Table 5). While cocaine is the most pervasive drug in all regions (84-98% of respondents in each region), heroin use is particularly widespread in Montreal (53% of 3,994 respondents), as is dilaudid in Quebec City (10% of 2,420 respondents), non-prescription morphine in Ottawa (35% of 1,367 respondents), and PCP in Saguenay-Lac-Saint-Jean (28.5% of 186 respondents).

There are also significant differences in injection drug use by age (Table 7). For example, heroin use was reported by 60% of injection drug users (IDUs) aged 24 or less (1,465/2,461) and by 27% of older IDUs (1,697/6,234).

A majority of the persons recruited also use non-injection drugs (Table 6; 2003-04 data). More than three-quarters of 1,124 respondents reported having used alcohol (83%) and cannabis (76%), while half had smoked crack (57%) and inhaled cocaine (53%).

While alcohol and cannabis use is widespread in all recruitment sites, non-injection drug use varies (Table 6; 2003-04 data). For example, PCP use was reported by only 10% of IDUs recruited in Ottawa (20/210), but by 28% of those recruited in Montreal (156/560).

In terms of non-injection drug use by age (Table 8), PCP, cannabis and amphetamines appear to be more popular among those aged 24 or less, while benzodiazepines are favoured by older users. Cocaine and crack use was comparable in both age groups (Table 8; 2003-04 data).

The injection site used by the largest number of IDUs during the previous six months was their own apartment (55%); the street was the most common injection site for 18% of recruited IDUs (98/559) (Table 15; 2003-04 data).

Levels of behavioural risk are generally higher among urban IDUs, both in terms of drug use (Table 16) and sexual behaviour (Table 20). Urban IDUs are more often long-term users, as well as more regular in their use, and are more inclined to inject drugs with strangers. Men recruited in urban areas are also more likely to report having had sex with other men, while urban women are more likely to report involvement in the sex trade.

However, use of needles and other supplies that have previously been used by others is more common among semi-urban IDUs. The latter are also more likely to obtain needles and other materials from people they do not know (Table 16).

Condom use by women (Table 18) and men (Table 19) is too infrequent to have a protective effect (be it with regular or casual partners, or with clients in the case of sex-trade workers).

Close to one man in 10 (613/6,522) and one women in two (917/2,114) reported having worked as a prostitute (Table 20).

The prevalence of human immunodeficiency virus (HIV) infection is 15% (1,310/8,899). Among IDUs aged 40 or more, one individual in four is already infected (Table 21).

The prevalence of hepatitis C virus (HCV) infection is 65% (725/1,116). Among IDUs aged 40 or more, four individuals in five are already infected (Table 22; 2003-04 data).

HIV prevalence is highest in Montreal, Ottawa and Hull, at close to 20% (Table 23).

HCV prevalence is 67% (95% CI = 64-70%) in urban areas, and 49% (95% CI = 40-59%) in semi-urban areas (Table 25; 2003-04 data).

HIV prevalence, based on initial participation in the study, remained stable over time throughout the network (Figure 1). It rose slightly in Quebec City and decreased in Ottawa.

The incidence rate of HIV is 3.5 per 100 person-years (PY). It is 4.5 per 100 PY in Ottawa/Hull, 4.3 per 100 PY in Montreal, 2.7 per 100 PY in Quebec City, and 1.8 per 100 PY in semi-urban programs (Table 32).

HIV incidence rates decreased consistently throughout the network until 2001 (Figure 2). Since then, an increase has been observed in Quebec City (since 2002) and Montreal (since 2001). However, observations recorded in 2003 remain to be confirmed, since follow-up data will be added for a number of individuals in the coming months.

Needle sharing remains the primary risk factor for HIV transmission. Cocaine as the most frequently injected drug, injection with strangers, older ages, and recruitment in Montreal are also independently associated with a higher risk of becoming infected (Table 33).

The proportion of those who reported having borrowed needles in the past six months decreased significantly in Montreal and Ottawa. A downward trend can also be observed in Quebec City, although this proportion increased between 2001 and 2003. No decrease was observed in semi-urban recruitment sites, where rates of needle sharing are highest (Figure 3).

The trends observed for risk factors associated with a higher incidence of HIV vary considerably from one recruitment site to the next (figures 7 to 10).

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