CONVALIDACION SECTOR AGROPECUARIO

The most efficient transmission of HCV is through large or repeated direct percutaneous exposure to blood 54_{. HCV is less efficiently transmitted by single small}

dose percutaneous exposures. Risk factors associated with acquiring infection include transfusion of blood or blood products, injecting drug use, unsafe therapeutic injections, occupational exposure to blood, birth to an infected mother, sex with an infected partner and sex with multiple partners. Epidemiological studies on the role of potential risk factors, such as medical procedures, injections for medications and immunisations, injecting drug use, tattoos and in a minority of cases, sexual transmission, have shown wide geographical variations 55_{. In developed countries, the}

prevalence of anti-HCV among persons who inject drugs (PWID) ranges from 31%- 98% 56_{. In developing countries, HCV transmission is mainly by contaminated blood}

products.

2.6 Epidemiology

It is now well established that HCV is of global importance and presents significant disease burden 52_{. The World Health Organisation (WHO) declared HCV a global}

health problem due to its impact on morbidity and mortality. Only a small proportion of those infected receive antiviral treatment, and up to half of those are unaware of this infection. Reasons for this include lack of awareness and knowledge of HCV among healthcare providers, at-risk patients, health policy-makers and the public. This contributes to poor screening services and missed opportunities for diagnosis, prevention and treatment 43_.

In 2010, the Global Burden of Diseases, Injuries and Risk Factors study was undertaken to estimate the burden of HCV infection 4_{. Since 1990, the numbers with}

HCV antibodies has risen from 122 million to over 185 millions. The prevalence of HCV demonstrates considerable geographical variation, which may be explained by different distributions and different contributions of risk factors in different study regions (Table 1) 4, 51_{. Although prevalence is highest in Egypt, China has the most infected individuals}

with 29.8 million 57_.

Table 1: Example of the variation in the global prevalence of HCV-RNA Country Viraemic Prevalence (%)

Asia Japan 1.1 China 0.8 Pakistan 5.8 Australasia Australia 1.2 Europe Romania 2.9 United Kingdom 0.4 Ireland 0.8 Italy 1.5 Latvia 1.7 Africa Egypt 10 Morocco 1.1 Latin America Brazil 1.3 North America United States 1

A recent study in Europe estimated that the prevalence of HCV varies between 2.4% for Western and Central Europe and 2.9% for Eastern Europe. With a global population of 740 million, it is estimated that the pool of HCV infected individuals in Europe is 19 million 58_.

2.6.1 HCV in Ireland

In Ireland, HCV is recognised as a significant public health problem yet the prevalence is poorly characterised. It is likely that there are many infected patients whom remain undiagnosed. HCV became a notifiable disease in Ireland in 2004. Cases are reported to the Health Protection Surveillance Centre (HPSC) through the Computerised Infectious Disease Reporting (CIDR) system. There have been over 14,000 cases of HCV notified in the 10 year period between 2004 and 2014 59_{. The number of cases}

notified reached a peak in 2007 and has steadily declined since with 710 cases notified in 2014 (Figure 2).

Figure 2: Number of cases of HCV notified between 2004-2014

Sourced from the Health Protection Surveillance Centre59

A collaborative study between the HSPC and the National Virus Reference Laboratory (NVRL) to estimate the prevalence of the infection in Ireland was published in 2012 5_.

Specimen-based laboratory data, for the period of 1989-2004, was translated to person-based data and combined with notification data from 2004-2009. From this, it was estimated that some 20,000-50,000 people in Ireland are chronically infected with

HCV, which equates to a population prevalence of 0·5-1·2%, with the majority yet to be diagnosed. This was similar to the prevalence estimates in other Northern European countries. However, these estimates are subject to uncertainty and the true prevalence rate of HCV in Ireland is unknown. This study also estimated the genotype profile of HCV-infected patients and it was established that GT1 accounted for 55% of HCV infections in Ireland 5_{. GT3 accounted for 39%, 4% were GT2 and 1% were GT4.}

The main causes of HCV in Ireland are injecting drug use and receipt of contaminated blood or blood products 5_{. Studies in Ireland among PWIDs, between 1992 and 2006,}

reported a HCV antibody prevalence of between 52-84% 60-66_.

2.6.1.1 Irish Legacy Cohort

October 1991 saw the commencement of routine screening for HCV antibodies in blood donors in Ireland 67_{. A regional study of donors completed in early 1994 identified}

14 men and 15 women with HCV antibodies. It was noted that the 15 women differed substantially from the overall donor population. These women were older and 87% were Rh-negative, compared to 18% in the general population. Administration of anti-D immune globulin to Rh (D) negative women who have delivered Rh (D) positive babies is a vital part of obstetric care. Twelve of these women had received anti-D immune globulin in 1977. Subsequent analysis of batches of anti-D immune globulin, used in Ireland to prevent Rh isoimmunisation was found to be contaminated with HCV (GT1b) from a single infected donor 67_.

presented for screening. Of these, 704 had evidence of past or current infection with HCV and 390 tested positive for serum HCV RNA 67_{. All of these women were referred}

to one of six hepatology centres throughout the country.

A second outbreak of HCV virus occurred between 1991 and 1994 as a result of administration of IV anti-D immune globulin batches manufactured in Ireland 68_{. A total}

of 44 women exposed to these batches of immune globulin were positive for HCV- RNA. Overall, approximately 1700 people infected with HCV through blood or blood products have been identified.