The aim of the study was in the differential specific diagnosis of viral infections of unknown etiology in patients who have recently returned from a trip to the countries of Southeast Asia and India. In 2013, SRC VB "Vector" examined single serum samples from 131 patients with suspected Dengue Fever. Dengue viral RNA was detected by means of polymerase chain reaction, NS dengue virus antigen and antibody classes M and G to Dengue virus - with the use of immunochromatographic methods and enzyme immunoassay. In the same sera the presence of specific IgM to measles, rubella and cytomegalovirus virus antigen was revealed by enzyme immunoassay and enzyme-enhanced chemiluminescence. As a result of examination 87 (66.4%) ofsamples were diagnosed as "Dengue fever". In seven out of the 87 samples there were detected specific class-M antibodies to cytomegalovirus. 44 sera (33.6%) out of 131 did not contain markers for Dengue fever. But 4 out of them contained IgM to measles virus, the other 5 sera contained IgM to rubella virus. Regional Centre of WHO laboratory confirmed three cases of measles, the one positive result for the content of IgM to rubella virus antigens results was interpreted as "equivalent." Identified in 2013 cases of importation ofmeasles and rubella by tourists from Southeast Asia and India have not resulted in the transmission of the disease through contact with others persons in Russia. In seven detected Dengue Fever cases opportunistic cytomegalovirus infection was revealed.