gms | German Medical Science

Background: A sensitive, specific and rapid laboratory diagnosis of SARS-CoV is important for the analysis of appropriate containment measures to be applied to each patient and his contacts, during an epidemic, in an attempt to prevent the transmission of the virus.

Procedures were established assuring that a laboratory diagnosis was reported very rapidly and that it included the diagnosis for the presence of other respiratory viruses that could be in the origin of the symptoms.

Laboratory procedures: From late March to late September 2003 a total of 64 specimens from 18 patients was received for SARS-CoV diagnosis, consisting of, at least, one or two upper respiratory track specimens together with blood and urine and/or faeces for each patient. All specimens were received packed according to WHO recommendations/regulations and processed in BSL 3 facilities.

Two in-house real-time RT-PCR protocols were implemented, and later validated by a quality assurance program from the WHO and ENIVD, for the diagnosis of SARS-CoV infection, one targeted to the nucleoprotein gene and the other to the replicase gene. All specimens, except serum and plasma, were real time RT-PCR tested for SARS-CoV, prepared for electronic microscopy, cell cultured for virus isolation and subjected to PCR testing for Influenza virus, Adenovirus and Respiratory Syncytial Virus at the time of their reception. Serum specimens were sent to the Health Protection Agency (England, UK) for anti-SARS-CoV antibodies testing.

Results: All patients were negative for SARS-CoV infection and seven were positive for other respiratory viruses. One patient tested positive for RSV B, two other for adenovirus, one for influenza AH3 and one for influenza AH1 (genetic and antigenic characterisation of influenza isolates will be presented). One patient tested positive for both influenza AH3 and adenovirus, and one for both influenza B and RSV B. No SARS-CoV-like particles were observed by electronic microscopy and all serological tests were negative.

Discussion: The procedures developed and applied allowed the diagnosis for SARS-CoV infection to be achieved within 3-5h and the diagnosis of other respiratory viruses within 1-2 days upon specimen reception. The isolation of infecting viruses in cell cultures confirmed the positive results obtained by molecular-based methods and extends the ability to detect infection by other viruses. There were no laboratory confirmed cases of SARS-CoV infection in Portugal and the celerity of the procedures implemented provided essential information to the decision-making process concerning to which containment measures should be applied, discarded or adapted to all patients during this period.