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The epidemiology and control of hepatitis C infection

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Hepatitis (inflammation of the liver) has many causes, such as specific bacterial and viral infections and certain toxic agents. Viral infections are one of the most common causes of hepatitis. Hepatitis C is a blood-borne virus and was first identified in 1989. It is significant since a large proportion of people infected go on to become chronic carriers of the virus. These individuals are at risk of long-term complications of chronic infection, such as cirrhosis and primary liver cancer.

Abstract

 

VOL: 99, ISSUE: 31, PAGE NO: 24

Usha Gungabissoon, BSc, is associate scientist, Immunisation Division, Health Protection Agency Communicable Disease Surveillance Centre, London

 

Hepatitis (inflammation of the liver) has many causes, such as specific bacterial and viral infections and certain toxic agents. Viral infections are one of the most common causes of hepatitis. Hepatitis C is a blood-borne virus and was first identified in 1989. It is significant since a large proportion of people infected go on to become chronic carriers of the virus. These individuals are at risk of long-term complications of chronic infection, such as cirrhosis and primary liver cancer.

 

 

The hepatitis C virus (HCV) was a significant cause of post-blood-transfusion non-A non-B hepatitis before its identification in 1989. Transmission of suspected non-A non-B hepatitis was most commonly associated with blood transfusions, although community infections were also recognised (Alter, 1995).

 

 

Global epidemiology
HCV is a global public health problem and a major cause of chronic liver disease worldwide. The World Health Organization estimates that 170 million people are chronically infected globally (WHO, 1999). It has estimated the global prevalence of HCV to be 3 per cent, with marked variation between countries. The prevalence of antibodies to HCV ranges between 0.4-2 per cent in most developed countries. Higher levels have been seen in parts of eastern Europe and Africa, where Egypt has been shown to have one of the highest levels. England and Wales are considered to have a low prevalence of infection, and the prevalence of chronic infection has been estimated to be 0.4 per cent (DoH, 2002a).

 

 

In developed countries, the majority of infections have been acquired through injecting drug use or receipt of a contaminated blood transfusion or blood products. These last two routes of transmission have been prevented in many countries by the introduction of donor screening and viral inactivation processes. Seroprevalence studies have shown consistently high prevalence in injecting drug users, ranging from 31-98 per cent (Memon and Memon, 2002).

 

 

Clinical features
Acute symptomatic HCV infection is rare and approximately 80-85 per cent of those who acquire the virus become chronically infected. Symptoms during the acute phase of infection may include nausea, vomiting, fatigue, jaundice and anorexia. As the majority of infections are asymptomatic many remain undiagnosed. Individuals who become chronic carriers are at risk of developing the long-term complications associated with infection.

 

 

The rate of progression of the disease is slow. From the point of infection to the appearance of cirrhosis and primary liver cancer may take up to 20 and 30 years respectively. A recent study found that HCV infection did not have a great impact on all-cause mortality in the first decade of infection. However, infected patients had an increased risk of dying from a liver-related cause, particularly those who consumed excess alcohol (Harris et al, 2002).

 

 

Mode of transmission
The virus is transmitted by blood-to-blood contact. This includes transfusion from infected blood or contaminated blood products. In developed countries, transmission is mainly though injecting drug users sharing blood-contaminated injecting equipment. Contaminated needles, syringes and associated equipment are, therefore, important in the spread of the virus. Other less common routes of transmission include sexual intercourse, transmission from a mother to child during birth and by skin piercing and tattooing if sterile equipment is not used.

 

 

Since 1991, blood transfusion services in the UK have routinely tested all blood donations for antibodies to HCV (anti-HCV). Prior to the introduction of viral inactivation of blood products in 1985 and the screening of blood donors, which started in 1991, some recipients of blood and blood products were inadvertently infected. Currently, the risk of transmission of hepatitis C by donated blood that has passed all screening tests is low. It has been estimated as being one in 30 million since the introduction of testing of HCV RNA in 1999 (Soldan et al, 2003). These interventions have greatly reduced the risk of HCV being acquired from blood or blood products.

 

 

Laboratory surveillance
Surveillance of HCV in England and Wales has been carried out by the Communicable Disease Surveillance Centre (CDSC) since the early 1990s (Ramsay et al, 1998). Laboratory reports of confirmed HCV infection provide important information regarding infection trends in specific risk groups over time.

 

 

Routine surveillance information is derived from confirmed infections reported to the CDSC by laboratories in England and Wales. Currently available serological assays are unable to differentiate between acute and chronic HCV infection. Information on probable route of acquisition and basic demographic information such as age, sex, and region of report are collected (Ramsay et al, 1998).

 

 

Between 1992 and 2002 a cumulative total of 33,316 reports have been received from laboratories in England and Wales (Fig 1). These confirmed reports show that the infection is more common in males than females, with a ratio of approximately 2:1. The majority of reports are in those aged 25-44 years. Risk factor information was available for one-third (11,465) of reports over this 11-year period. Injecting drug use is the most commonly reported risk factor, accounting for 90 per cent where a risk factor is known. Other reported risk factors include receipt of blood products or a blood transfusion.

 

 

Occupational exposure in health care
Health care workers may be at greater risk of HCV than the general UK population. The overall prevalence has been estimated to be 0.23 per cent among all health care workers and 0.28 per cent in those at risk of occupational contact with blood and body fluids (Ramsay, 1999). However, the risk of transmission from an infected health care worker to a patient is considered low.

 

 

Current guidelines state that health care workers found to be carrying the virus (those who are HCV RNA positive) should not be allowed to perform exposure-prone procedures (DoH, 2002b). Those who have antibodies to the virus and are HCV RNA negative should be allowed to continue performing exposure-prone procedures. Health care workers who are positive for HCV RNA or antibody to hepatitis C should be referred to a liver specialist for assessment and consideration for treatment.

 

 

Health care workers exposed to known infected sources should be followed up at six, 12 and 24 weeks after exposure (Ramsay, 1999). Management of those exposed to a source whose HCV status is unknown or a source unavailable for testing will depend upon a risk assessment by a designated doctor. In order to assess the numbers of health care workers being exposed in the occupational setting, the CDSC is conducting a national surveillance of occupational exposure to blood-borne viruses in health care workers. This seeks to record all cases of significant occupational exposure such as incidents of percutaneous or mucocutaneous exposure, with blood or other fluids involving patients known, or subsequently found to be, infected with HIV, HCV, or hepatitis B.

 

 

There is no recommended post-exposure prophylaxis for hepatitis C. However, a recent study suggested that early treatment of acute infection with interferon alpha prevents chronic infection (DoH, 2002b).

 

 

Treatment
Interferon alpha has been widely used to treat chronic HCV infection, although better response rates have been seen when it has been used in combination with ribavirin. National Institute for Clinical Excellence (NICE) guidelines recommend that interferon alpha and ribavirin be given as combination therapy in cases of moderate-to-severe infection to those aged 18 years and over (NICE, 2000). This therapy is not recommended for treatment in heavy users of alcohol because of an increased risk of exacerbation of liver damage or in those who continue to inject drugs. Interferon alpha and ribavirin should be offered in combination to all previously untreated infected individuals. Combination therapy response rates range from 50 to 60 per cent.

 

 

Prevention
There is no vaccine to protect against HCV infection. Universal precautions apply to prevent its transmission. All blood, body fluids and body tissues should be treated as potentially infectious at all times.

 

 

Injecting drug users are at high risk of HCV infection, and prevention strategies should be targeted at this group. Preventing the sharing of injecting equipment and minimising other risk procedures associated with injecting are essential for controlling HCV infection.

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