In Latin America, the overall prevalence of HCV infection is about 1.23%, however it varies from country to country
[20, 21]. In Brazil, the prevalence of HCV infection is around 1.38%. In addition, significant differences in the prevalence of infection and distribution of HCV genotypes among Brazilian regions are reported. The northern of Brazil (Brazilian Amazon) stands out with the highest prevalence of infections and higher frequency of genotype 1
[20, 22, 23]. Among the risk groups for infection, illicit-drug users make up the main risk group for HCV infection in Brazil
A consensus now exists that the use of non-injected drugs is a risk factor for the hepatitis C virus. Risk levels appear to vary substantially by location
[5, 6, 24–26]. HCV prevalence in non-injecting drug users range from 2% to 38% in different parts of the world
[3, 8, 11, 27–29]. Epidemiological studies of illicit-drug users in the Northeast, Midwest, South and Southeast regions of Brazil (including both injecting and non-injecting drug users) have recorded prevalence of HCV infection between 5% and 36%
[9–14]. The HCV prevalence recorded in the present study is within these estimated ranges, although the rate of HCV infection among non-injecting drug users in Pará was relatively high compared with the rates obtained in similar populations in different parts of the world, and extremely high and worrisome compared to the reported rates of HCV infection in other Brazilian regions. The marked prevalence of HCV-RNA in the drug-user population studied here should serve as an incentive for the establishment of a program of Hepatitis C prevention and control by the local public-health authorities. This program should include the use of non-injected drugs as a potential risk factor for transmission of HCV infection. Given the important consequence of this finding, more research on this topic is warranted in eastern Amazon.
The mechanisms of HCV transmission among non-injecting drug users are not well understood
. This study identified six risk factors for HCV infection. Having a tattoo was associated with HCV infection. Commonly, a tattoo is identified as a risk factor for HCV infection in illicit-drug users
[2, 6, 8]. Likely, this reflects the lifestyle of illicit-drug users, which could include greater exposure to HCV. Furthermore, the daily use of drugs, paraphernalia sharing during drug use, and a long history of drug use were also associated with HCV infection in non-injecting drug users. Few studies have reported the presence of HCV-RNA in the nasal secretions of cocaine and crack users, indicating a possible alternative route for the transmission of the virus – the sharing of the paraphernalia used to consume these drugs
[4, 30]. One hypothesis to account for these cases involves intranasal transmission of HCV via contaminated implements, requiring two primary virological preconditions: the presence of blood and HCV in the nasal secretions of intranasal drug users, and the transfer of blood and HCV from the nasal cavity onto sniffing implements, which are often shared by intranasal drug users
[4, 30]. In Pará, HCV transmission may be associated with and powered by three risk factors: daily use of drugs, paraphernalia sharing during drug use, and a long history of drug use (more than 5 years). To prove this hypothesis, other, more-specific studies will be needed in the future.
Other risk factors for HCV infection identified in this study were age above 35 years, and use of a needle and glass syringe sterilized at home. Administering injectable medication without adequately sterilizing syringes or needles has been the main cause of HCV transmission worldwide, especially in developing countries
[1, 31, 32]. In Brazil, disposable perforating and cutting materials for health procedures began to be used on a large scale during the second half of the 1980s. This situation, together with a lack of knowledge about HCV transmission, likely accounts for the higher prevalence of infection among Brazilians over 35, since transmission could have occurred through sharing of inadequately sterilized syringes and needles in homes with individuals who were asymptomatic and unaware that they were infected. Probably the risk factor “use of home-sterilized syringes and needles” was partly responsible for the significantly higher infection rate in the group older than 35 years. This may also indicate that longer exposure to risk factors increases the probability of infection with HCV. These two risk factors for HCV infection have also been detected in other Brazilian populations, including blood donors in the Brazilian state of Pará
[12, 15, 17, 33].
In Brazil, HCV genotype 1 predominates, followed by genotypes 3 and 2
[23, 34]. In the Brazilian Amazon, HCV genotype 1 prevails in blood donors, health-care workers, illicit-drug users, patients with chronic hematological disease, and patients undergoing hemodialysis
[12, 15, 17, 18]. The results of the present study were well within this range, with a high frequency of HCV genotype 1 (1a and 1b) and the presence of genotype 3 (3a and 3b). This study also showed that in a geographic area in which the populations are predominantly infected with genotype 1, a relatively high frequency of genotype 3 can also occur
[15–17, 34]. This study concords with the finding of several other studies that reported the existence of a significant frequency of genotype 3 in illicit-drug users, reflecting the intrinsic characteristic of network transmission through sharing of illicit drugs and abuse of their paraphernalia
[11, 12, 18, 35, 36].
The present study has limitations that should be considered in the interpretation of results. No procedures for identifying injection drug use, including those used in this study, are foolproof. The number of non-injecting drug users and their general characteristics in the state of Pará are not actually known since drug use is an illicit activity. For that reason, HCV infection was only investigated among those non-injecting drug users enrolled in private and public drug treatment centers during the study period. On the other hand, given the scarcity of epidemiological data about HCV infection among illicit-drug users in the state do Pará, our results provide background information for formulating policies and strategies for reducing risk and damage associated to the use of illicit drugs. Furthermore, the specific sexual behavior of illicit-drug users in detention was not investigated. Some studies suggest that illicit-drug use and sexual behavior during detention may be associated with HCV infection
[28, 37]. Finally, the 5’ UTR contains sufficient variation to resolve HCV classifications at the level of viral genotype. However, it is conserved and limited in its ability to discriminate subtypes within genotypes 1, 2, 3, 4, and 6
. Thus, there is a need for sequencing of other regions of the HCV genome to improve the resolution of viral subtypes.