[Application of the polymerase chain reaction (PCR) to diagnosis in virology].

Recall of the principle of the PCR and of its advantages: rapidity, possible automatization, high sensitivity allowing the detection of minute amounts of infectious agents, specificity depending on that of the primers used for the detection of the amplified product. But this technic has to be used with care to avoid any contamination which might give false positive results and requires controls. This procedure would allow to analyze the evolution and the variability of infectious agents by their sequence determination, thus providing a powerful tool for molecular epidemiology investigations. This method has already been used in many diagnoses of viral infections. The authors show results obtained on dengue viruses: 24 out of 32 sera were found positive (75%) by PCR whereas only 15 (47%) were positive by cell culture. On the other hand, 7 strains of dengue 2 virus of various regions throughout the world and isolated between 1969 and 1982 showed extensive degrees of variability.