Advances in Virology Volume 2012 (2012), Article ID 205085, 7 pages doi:10.1155/2012/205085Research Article Association of Active Human Herpesvirus-6, -7 and Parvovirus B19 Infection with Clinical Outcomes in Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Svetlana Chapenko,1 Angelika Krumina,2 Inara Logina,3 Santa Rasa,1 Maksims Chistjakovs,1 Alina Sultanova,1 Ludmila Viksna,2 and Modra Murovska1 1August Kirchenstein Institute of Microbiology and Virology, Riga Stradins University, Ratsupites Street 5, LV-1067 Riga, Latvia 2Department of Infectology and Dermatology, Riga Stradins University, Linezera Street 3, LV-1006 Riga, Latvia 3Department of Neurology and Neurosurgery, Riga Stradins University, Pilsonu Street 13, LV-1002 Riga, LatviaReceived 2 March 2012; Revised 21 June 2012; Accepted 28 June 2012Academic Editor: Julia G. Prado Copyright © 2012 Svetlana Chapenko et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 2 March 2012; Revised 21 June 2012; Accepted 28 June 2012 Full paper: http://downloads.hindawi.com/journals/av/2012/205085.pdf Abstract: http://www.hindawi.com/journals/av/2012/205085/ Abstract Frequency of active human herpesvirus-6, -7 (HHV-6, HHV-7) and parvovirus B19 (B19) infection/coinfection and its association with clinical course of ME/CFS was evaluated. 108 ME/CFS patients and 90 practically healthy persons were enrolled in the study. Viral genomic sequences were detected by PCR, virus-specific antibodies and cytokine levels—by ELISA, HHV-6 variants—by restriction analysis. Active viral infection including concurrent infection was found in 64.8% (70/108) of patients and in 13.3% (12/90) of practically healthy persons. Increase in peripheral blood leukocyte DNA HHV-6 load as well as in proinflammatory cytokines' levels was detected in patients during active viral infection. Definite relationship was observed between active betaherpesvirus infection and subfebrility, lymphadenopathy and malaise after exertion, and between active B19 infection and multijoint pain. Neuropsychological disturbances were detected in all patients. The manifestation of symptoms was of more frequent occurrence in patients with concurrent infection. The high rate of active HHV-6, HHV-7 and B19 infection/coinfection with the simultaneous increase in plasma proinflammatory cytokines' level as well as the association between active viral infection and distinctive types of clinical symptoms shows necessity of simultaneous study of these viral infections for identification of possible subsets of ME/CFS.