The emergence and spreading of new exotic viral diseases is most probably caused by the destruction of the tropical biosphere and, furthermore, due to the genetic variation of virus virulence, tropism and adaptation to other species (breaking the species barrier). An efficient control of such viral infections requires constant collaboration of medical and veterinary scientists. Some new presented data concern: identification of interferon-producing cells; RNA vaccine on flavivirus model; training viruses to attack cancer; neuraminidase inhibitors - efficient anti-influenza drugs; Nipah virus of Malaysian epidemic; neurovirulence of porcine reproductive and respiratory syndrome virus; malignant catarrhal fever in pigs caused by ovine herpesvirus 0-2.