Epidemiology, risk factors and possibilities for the prevention of acute leukaemia.

Acute leukaemias are malignant diseases of haematopoiesis, traditionally classified according to the affected cell line as acute lymphoblastic and acute myelogenous leukaemia. In terms of incidence, acute leukaemias are rare diseases - in the Czech Republic, only 2-3 new acute myelogenous leukaemia cases/100 000 population are diagnosed annually and less than 1 new case of acute lymphoblastic leukaemia/100 000 residents. The causes of acute leukaemias are still poorly understood. The established risk factors are age, ionizing radiation or Downs syndrome. Moreover, a number of potential risk factors have been described to play a role in development of acute leukaemias and to multiply the risk, such as physical factors, chemicals, genetic and familial predispositions or other diseases. The presented review summarizes the knowledge of the aetiology of acute leukaemias published since 2000. It describes their epidemiological characteristics and risk factors and outlines the possibilities for their prevention.

Epidemiology of hepatitis E virus infection.

Hepatitis E is a major concern to public health, it is estimated that 44,000 people die annually due to hepatitis E. Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis in the world. HEV has been found with 7 genotypes, only 4 can infect humans. Genotypes 1 and 2 are major causes of the epidemic and endemic acute hepatitis in developing countries. In the poor hygienic conditions, these genotypes are obligate human pathogens transmitted between humans by the fecal-oral route and via contaminated water. On the contrary, in developed countries, genotypes 3 and 4 are of zoonotic origin and they are transmitted by alimentary route and via direct contact with the infected animal. Transmission by blood, blood products and tissues from infected persons or animals and even mother-to-infant transmission is also possible. Hepatitis E clinical course varies from self-limiting disease to fulminant hepatic failure, and extrahepatic manifestations have occurred. Management to control and prevent this infection is mainly hygienic measures. The provision of clean drinking water and ameliorating the sanitation of human wastes are the most effective preventive approaches as in any infection outbreak transmitted through the fecal-oral route. Nevertheless, dietary habits, distribution of different zoonotic reservoirs and the hygienic level play a crucial role in limiting and preventing the spread of hepatitis E in the developed countries. Although HEV vaccine was developed, it is still available only in China. It protects against genotype 4 with no clear evidence of protection against other genotypes.