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Infectious Diseases


Hepatitis is the inflammation of the liver caused by one of five currently identified hepatitis viruses (A, B, C, D and E). All of these viruses can cause an acute disease with symptoms lasting several weeks including yellowing of the skin and eyes (jaundice), dark urine, extreme fatigue, nausea, vomiting and abdominal pain.

Hepatitis A virus is spread from person to person by putting something in the mouth that has been contaminated with the stool of a person with hepatitis A. This type of transmission is called "faecal-oral." For this reason, the virus is more easily spread in areas where there are poor sanitary conditions or where good personal hygiene is not observed. Most infections result from contact with a household member or sex partner who has hepatitis A. Casual contact, as in the usual office, factory, or school setting, does not spread the virus.

Hepatitis B (HBV) is transmitted by direct contact with the blood or body fluids of an infected person. HBV is not spread through food or water or by casual contact. HBV carriers are people who are have chronic (long-term) infection with HBV and never recover fully from the infection; they carry the virus and can infect others for the rest of their lives. In the United States, about one million people carry HBV.

Hepatitis D (HDV) is dependent on HBV for replication. HDV infection can be acquired either as a co-infection with HBV or as a superinfection of persons with chronic HBV infection. Persons with HBV-HDV co-infection may have more severe acute disease and a higher risk of fulminant hepatitis (2%-20%) compared with those infected with HBV alone. Chronic HBV carriers who acquire HDV superinfection usually develop chronic HDV infection. In long-term studies of chronic HBV carriers with HDV superinfection, 70%-80% have developed evidence of chronic liver diseases with cirrhosis compared with 15%-30% of patients with chronic HBV infection alone. The modes of HDV transmission are similar to those for HBV.

Hepatitis E (HEV) is transmitted primarily by the faecal-oral route and faecally contaminated drinking water is the most commonly documented vehicle of transmission. Risk factors for infection among persons with sporadic cases of hepatitis E have not been defined. Unlike hepatitis A virus, which is also transmitted by the faecal-oral route, person-to-person transmission of HEV appears to be uncommon. Virtually all cases of acute hepatitis E in developed countries have been reported among travellers returning from high HEV-endemic areas.

Prevalence & Incidence

The following maps are from Centers for Disease Control and Prevention (CDC), Atlanta, USA

Hep A

Hep B

Hep D

Hep E

Economic Cost

Hep A

Although most infected persons recover completely and a significant proportion remain asymptomatic, HAV infection causes considerable morbidity and mortality and imposes a large economic burden throughout the world. According to the WHO, there are an estimated 1.4 million cases worldwide of acute HAV which cost US$1.5 to US$ 3 billion annually.

Hep B

The WHO estimates that 400 million people worldwide are already chronically infected with HBV and 10 to 30 million people become infected annually. In China, where 10% of the population is chronically infected with HBV, direct economic losses caused by viral hepatitis were more than US$6 billion in 2001. In the United States, treatment costs of hepatitis B virus infection are estimated at US$720 million annually.