Methods and techniques to increase the reliability of detecting virus infections, particularly lymphotropism, to eliminate false negative reactions in testing blood for the presence of lymphotropic viruses during enzyme immunoassay (EIA) and polymerase chain reaction (PCR) testing, and to better detect viruses with lymphotropism in biological materials having a concentration of virus particles lower than the sensitivity threshold of existing EIA and PCR methods, thereby making the techniques of the present invention more reliable.