The use of a reverse transcription-polymerase chain reaction for the detection of viral nucleic acid in the diagnosis of Crimean-Congo haemorrhagic fever

Abstract

A reverse transcription-polymerase chain reaction (RT-PCR) was applied retrospectively to 80 stored serum samples from 45 confirmed Crimean-Congo haemorrhagic fever (CCHF) patients in southern Africa, and it was found that viral RNA could be detected in a proportion of samples up to day 16 of illness. Early in the disease there is relatively good correlation between the results obtained by RT-PCR and virus isolation, but after the first week it appears that infective virus is progressively cleared from serum while nucleic acid remains demonstrable in a proportion of patients well into convalescence. A further 47 serum samples from 38 patients with suspected viral haemorrhagic fever, 19 of whom proved to be cases of CCHF, were tested prospectively on being received at the laboratory. The combined use of RT-PCR with ethidium bromide stained gels for the detection of viral RNA, plus indirect immunofluorescence for the detection of IgG and IgM antibodies to CCHF virus, permitted a presumptive diagnosis to be reported within 8 h of receiving the first specimen from 18/19 cases of the disease studied prospectively. The nineteenth case was confirmed within 48 h when antibody response was demonstrated in a second serum sample. Viral nucleic acid was not detected in serum samples from 19 patients in whom alternative diagnoses were established.