Introduction

The Hepatitis C virus (HCV) is a leading cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma and an important global health problem [1]. Globally, it is estimated that 50 million people have chronic HCV infection, with about 1.0 million new infections occurring per year and in 2022 WHO also estimated that, approximately 242,000 people died from cirrhosis and hepatocelluar carcinoma caused by HCV [2]. HCV has high genetic diversity, has main 8 genotypes (GT) and 86 subtypes. The distribution of HCV GTs and subtypes varies based on geographical regions, countries, transmission routes and even in cultural groups. GT1, GT2 and GT3 is most common worldwide and most of the HCV infections are caused by these genotypes in Asia, Europe and North America [3]. While GT4 is most common in North, Middle East and Central Africa; GT 5, 7 and 8 is mostly seen in Southern and sub-Saharan Africa and GT6 occurs throughout Asia [3–5]. GT1 is the most common globally, with subtype 1a predominating in the United States and Canada, and subtype 1b is more prevalent in Europe [6]. These patterns reflect the diverse geographical spread and epidemiology of HCV, underscoring the importance of understanding regional prevalence for effective treatment planning and public health strategies [7]. In Turkey GT1, mostly GT1b is responsible for about 90% of HCV infections [8]. The determination of viral genotype is crucial in choosing antiviral treatment, determining the duration of the therapy, and monitoring treatment respose. Since 2014, with the usage of direct-acting antiviral agents (DAAs) in the treatment of HCV infections, a cure rate over 95% could be possible [9]. DAAs also have good safety profile and treatment with these drugs are shorter. But again it is crucial to determine the viral load, GT and the clinical status of the patient. According to the Viral Hepatitis Fight Association, HCV treatment guideline, for GT1 subtype also should be determined; if subtype determination can not be made in patients with GT1, patients should be treated as if they were infected with G1a [10]. Rarely, mixed genotypes can be detected; in these cases, pangenotypic regimens should be preferred in treatment [10].

There are many reports about distribution of HCV genotypes, from different regions of Turkey but there is no central database and epidemiological data is obtained from local studies [11]. As we know GT distribution depends on many factors such as age groups, gender, geographical regions, countries, transmission routes and cultural groups. Due to its geographical location, Turkey is like a bridge connecting Asia and Europe. Istanbul is the biggest and most crowded city of Turkey and has received immigration from many different countries, especially Syria, in recent years and immigration still goes on. Also our hospital in Istanbul has serves a very large patient population (about 3 million patients/year) from many different nations. In addition, COVID-19 pandemic was intensely experienced in our country as well as the rest of the world. The primary purpose of this study is to explore and document the distribution of HCV genotypes among patients diagnosed with Hepatitis C infection in Istanbul, Turkey, at Health Sciences University Ümraniye Training and Research Hospital over the period from 2016 to 2022. Our hospital's data on HCV genotypes and comparing them with historical data will serve as a great mirror for HCV epidemiology in Turkey and will also contribute to data in the world. In addition, since our study covers the years 2020–2022, it has the potential to show whether the COVID-19 pandemic, which was intensely experienced in our country as well as the rest of the world, has an impact on HCV epidemiology.

Materials and methods

In our research, we conducted a retrospective analysis of 322 patients who had their HCV genotypes determined from 2016 to 2022. Permission for the study was obtained from the Ümraniye Training and Research Hospital Clinical Research Ethics Committee. Each patient's unique genotyping result was included in the study. The detection of HCV-RNA positivity was carried out using the real-time PCR method (artus HCV QS-RGQ Kit, Qiagen, Germany), followed by genotype determination via the reverse hybridization line probe assay (LiPA) method (Nlm srl, Italy), in accordance with the manufacturer's guidelines. Statistical analysis was performed using IBM SPSS Statistics for Windows, Version 21.0 (Armonk, NY: IBM Corp.), released in 2012. The analysis involved descriptive statistics, including mean, maximum, and standard deviation. Group comparisons were conducted using the Fisher exact test, Pearson Chi Square test and multinominal logistic regression analysis. For non-normally distributed groups, the nonparametric k-independent sample Kruskal-Wallis test was applied, and the Mann-Whitney U test was used for the comparison of subparameters.

Results

In our study, we examined patients ranging in age from 7 to 88 years (average: 54.28, standard deviation: 16.79), consisting of 155 females (48.1%) and 167 males (51.9%). Out of 322 patients, 311 were found to have a single genotype, while 11 had 2 genotypes. Analysis of patients with a single genotype revealed that HCV GT1b was the most prevalent in 65.2%, followed by GT3 in 15.5%, GT1a in 10.6%, GT4 in 3.4%, GT2 in 1.5% and GT5 in 0.3% (Table 1). Patients with mixed genotypes constituted 3.4% of the total (11/322) with the following subtypes observed: 3/4 (4), 1b/1a (2), 1b/3 (1), 1b/4 (1), 2/4 (1), 2a/c (1), and 4c/d (1) (Table 1). When examining the distribution of genotypes over the years, GT1b was consistently the most common, followed by GT3. Genotypes 2, 4, and mixed types varied in prevalence across different years. Notably, GT5 was identified in just one patient, a foreign national from Syria, in 2017. In our analysis of the distribution of genotypes over the years, a significantly higher number of GT1a and GT1b cases were detected in 2017 compared to other years; in contrast, the year 2020 witnessed the lowest detection of this genotype (P = 0.023). The decrease in patient numbers in 2020 is possibly attributed to the COVID-19 pandemic period (Table 1).

When comparing genotypes with respect to gender, GT1 was found to be significantly higher in women, and GT3 was more prevalent in men (P = 0.032). According to regression analysis, the incidence of genotype 3 in men is 3.86 times higher than in women (P = 0.013) (Table 2).

Patients' clinical presentations, which were divided into categories such as liver transplant cases, cirrhosis, fibrosis, acute hepatitis, and chronic hepatitis, did not significantly correlate with any particular genotype (P = 0.221 for the Mann Whitney U test and the Kruskal-Wallis test) (Table 3).

In the distribution of genotypes according to age groups, GT1b was found to be significantly higher in those aged 60 and above, and GT3 was found to be significantly higher in those aged 30–49. The distributions in other age groups were not found to be statistically significant because the number distribution was non-parametric (Graphic 1).

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Genotype distribution according to age groups

Citation: Acta Microbiologica et Immunologica Hungarica 2024; 10.1556/030.2024.02388

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When we look at the distribution of genotypes according to nationality, totally 16.1% of our patients was foreign nationals. GT1b was the most common GT also among foreign nationals (61.5%). Only 17.3% (9\52) of foreign patients were from Syria and most of the others were from Turkish Republics, such as Turkmenistan, Uzbekistan, Kazakhstan, Kyrgyzstan. 2.9% (1/34) of GT1a, 15.2% (32/210) of GT1b, 20% (1/5) of GT2, 20% (10/50) of GT3 was foreign nationals. It was observed that 36.4% (4/11) of the patients with GT4 and 1 patient with GT5 were foreign nationals and Syrian (Table 4).

Discussion

The global distribution of HCV genotypes varies geographically. While GT1 is the most frequently identified worldwide (46–49%) and the most common subtype is GT1b; it is usually followed in prevalence by GT3 (17.9–30%) and GT2, GT4 and GT6 constituting about 23% of cases [1, 12]. Genotypes 5, 7, and 8 constitute less than 1% of global HCV infections [12]. The situation in Turkey is still consistent with world data, being the most common GT is GT1 and especially GT1b. According to various studies from Turkey, GT1 prevalence ranges between 51.7% and 97.1%; where as GT1b ranges between 52.7% and 97.4% [13]. Some studies over the years indicate that the prevalence of Genotype 1b has decreased over time [1, 14–17] although there are also publications suggesting that no significant change has been observed [9, 18]. In our study analysis of patients with a single genotype revealed that HCV GT1b was the most prevalent in 65.2%, followed by GT3 in 15.5%, GT1a in 10.6%, GT4 in 3.4%, GT2 in 1.5% and GT5 in 0.3%. In our study during 7 years period, GT1b was consistently the most common, followed by GT3. Genotypes 2, 4, and mixed types varied in prevalence across different years. The dominance of GT1 (75.8%), particularly subtype 1b, was consistent with global trends, followed by GT3 (15.5%) and smaller proportions of GTs 4, 2, and 5. Our data is also very similar with the data of Alacam and et al., from İstanbul, which has examined 546 patients between 2017 and 2020; and also with Bulut et al. who examined 385 patients in Istanbul between 2019 and 2021 [9, 13]. Our study and other studies has shown that GT1b is still the dominant GT in İstanbul and the epidemiology does not appear to have changed much either.

In our analysis of the distribution of genotypes over the years significantly higher number of GT1a and GT1b cases were detected in 2017 compared to other years; in contrast, the year 2020 witnessed the lowest detection of this GT (P = 0.023). Apart from the fact that the highest number of HCV genotypes were tested in 2017 and the decrease in the number of patients admitted to the hospital for non-COVID reasons in 2020, probably due to the COVID-19 pandemic, we could not identify any other feature. It is also seen that the number of patients was low in 2021 and 2022, the years when the pandemic has continued. Interestingly also in Alacam's study from İstanbul which covers the years 2017 and 2020, the rate of HCV viremia was highest in 2017 (52.36%) and lowest in 2020 (18.30%) and it was statistically significant but there was no significant difference between the detection rates of GTs by years [9]. However, even this data seems significant in terms of showing the negative impact of the COVID-19 pandemic on other health problems.

In our study 16.7% of patients was foreign nationals. In foreign nationals the most common GTs were 1b, 3, 4, 1a respectively and 5 and 2 was detected in 1 patient each. In Turkish patients the most common GTs was 1b, 1a, 3, mixed, 4 and 2. GT5 was detected in just one Syrian patient, in 2017. Statistical analysis could not be performed in this area because the number of patients was insufficient. Similarly, Alacam and et al. from İstanbul reported that, GT1b was the most common GT for both Turkish and foreign national patients; in Turkish the second and third most common GTs was 1a, 3 while in foreign nationals the second and third most common GTs was 1a and 4 [9]. Alacam et al. also reported that GT4 was significantly higher in foreign nationals but there is no information about the nationality or transmission routes in their study [9]. It is known that GT4 is mostly found in North Africa and the Middle east and also is associated with intravenous drug usage with GT1a and 3; also in Europe, most of the GT4d patients were male and intravenous drug users [4]. In our study GT4 was found in only 11 patients, 4 of them was from foreign nationals and 8 of the 11 patients were female. We know that 7 of them were Turkish patients and 4 of them was from Syria but we do not have any information about transmission routes. In recent studies it has been stated that HCV epidemiology has changed in Turkey and GT3 is more detected because of intravenous drug usage [19, 20, 21]. In our study GT3 and 1a are the second most common GTs and when comparing genotypes with respect to gender in our study, GT1 was found to be significantly higher in women, and GT3 was more prevalent in men. In a multicentral study from Turkey about HCV GT distribution among iv drug users, GT3 was the most commonly observed GT and most of the patients were male [21]. We do not know about the transmission routes of HCV in our study but it can be suggested that this may be related to the higher iv drug usage among male patients. This findings may indicate variations in exposure or susceptibility to distinct HCV genotypes based on gender, which calls for additional research.

Gökahmetoğlu et al. and Çetin Duran et al. suggested that in Turkey HCV infections are primarily associated with unsafe medical procedures, GT1b is the most common GT and more common in older women because of unsafe medical procedures [4, 22]. In our study the demographic composition included a nearly equal distribution of males (51.9%) and females (48.1%), ranging from 7 to 88 years old but when we look at the distribution of genotypes according to age groups, GT1b was found to be significantly higher in those aged 60 and above, and GT 3 was found to be significantly higher in those aged 30–49. Therefore, our data also supports these studies. The fact that GT3 has increased over the years and is more common both in men and in the 30–49 age group again brings to mind risky behaviors, especially iv drug use, and indicates that the transmission routes of HCV infection should be investigated more comprehensively in Turkey. Revealing the routes of transmission and raising people's awareness about this issue is one of the most important steps in preventing the spread of HCV infection, which is still an important public health problem.

Patients' clinical presentations, which were divided into categories such as liver transplant cases, cirrhosis, fibrosis, acute hepatitis, and chronic hepatitis, did not significantly correlate with any particular genotype. This discovery raises the possibility that variables other than genotype, including as patient demographics, concomitant diseases, and environmental factors, may have an impact on the clinical development of HCV infection.

In two studies about global distribution of HCV GTs, it is reported that specifically in Syria, GT4 is dominant and followed by GT1 but GT5 is less prevalent and is commonly found in South African countries [3, 22]. Murat et al. from Mersin investigated 302 patients between 2018 and 2022, and suggested that in 44 mainly Syrian and Ukrainian origin nationals GT4 was the predominant GT [11]. In a study from Gaziantep, which is a city in the border of Syria, 1,628 patients between 2013 and 2022 were analyzed retrospectively; GT1 was detected in 51.5%, GT3 in 21.4%, GT4 in 20%, GT 5 in 4.6%, and 29% of patients was from Syria [23]. In our study GT4 was detected in only in 11 patients and 4 of them was from Syria and 7 of them was Turkish patients. As we have stated before, İstanbul has received immigration from many different countries including Syria in recent years and continues to do so. Also our hospital in İstanbul serves a very large patient population (about 3 million patients/year). Considering that the dominant genotype in Syria is 4, GT4 could be expected to be detected in greater numbers within 6 years due to migration. This result made us think that since our study only evaluated patients who applied to the hospital, Syrians or other immigrants may not have been able to apply to the hospital and were not diagnosed for various reasons, such as not having health insurance. We think that in a country with intense immigration like Turkey, community-based, comprehensive studies should be conducted to evaluate the changing epidemiology of HCV and many other infectious agents. Another reason may be that people's applications to health institutions have decreased due to the pandemic. Again in the study from Gaziantep GT3 was detected in 277 (79.6%) male prisoners and they claimed that this may be about iv drug usage [23]. GT3 is also the 2. most common GT in our study. All these data about HCV seem to be important indicators for preventing the spread of the disease by determining the routes of transmission as well as diagnosis, genotyping and treatment.

In conclusion, our study and other studies show that HCV infection is still very important public health problem both in world and in our country. However, in countries like our country that receive uncontrolled immigration, it is highly likely that these data are just the tip of the iceberg. Considering that many immigrants still live in unhealthy conditions, cannot access the healthcare system, and the increasing bad habits in society such as iv drug use, it is of great importance to identify and treat patients by screening not only in patients applying to hospitals but also the whole society. Variations in genotype prevalence between the sexes that we found in our study point to a potential interaction between biological variables and transmission routes in HCV genotypes that should be investigated with more comprehensive community based studies. With the support of health authorities, informing the entire society about the seriousness of the disease and the ways of transmission is among the first measures to be taken. The data from our study also showed the importance of establishing a health system in which the diagnosis and treatment of all diseases and preventive health services can be maintained even in crisis situations that may affect the whole world, such as the COVID-19 pandemic.

Conflict of interest

All of the authors state that there is no conflict of interest.