Hepatitis A is a globally distributed disease caused by Hepatitis A virus. The virus is highly resistant in the environment and is transmitted fecoorally, which enables it to spread horizontally and via food and water. The clinical picture of hepatitis A varies from subclinical infection of children to severe, prolonged, icteric hepatitis of adults. A contact to the virus raises life-long immunity that prevents adults from becoming sick in endemic regions in developing countries. Due to increase of traveling, import of food and decreased population immunity, the risk of Hepatitis A outbreaks in Finland has increased. The risk can be controlled by hygienic and immunogenic measures.
West Nile virus is a flavivirus that causes encephalitis. The virus is widely distributed in Africa, Asia and Europe. West Nile virus is endemic in the Nile Delta area, which explains the name of the virus. The first actual epidemy in Europe occurred in Romania in 1996. In the United States West Nile virus was identified for the first time in August 1999. American health authorities are afraid of new epidemics and the possibility that the virus can spread even wider. West Nile virus has been isolated from humans, other mammals, birds and arthropods. Birds are the most important reservoir. Mosquitoes transmit the infection from birds to other animals and humans. Control of vector mosquitoes is essential in preventing the transmission of the virus. In areas where epidemics occur, it is important to reduce larvae in the standing water sources. The disease can be prevented by using pesticides and avoiding mosquito bites.