Reading between the line of the NY Times article, I think that Guangzhou is sounding more and more like Severe Chronic Respiratory Syndrome. One sample has tested positive by three different labs and I suspect that by now there is some sequence data and it is an exact match for SARS CoV in Guangzhou last March
Thus, the two simplest explanations were a re-activation of an old SARS CoV infection, or contamination. However, the antibody data would discount contamination, but WHO is considering a scenario similar to the one in Surrey. BC.
However, there are several important differences. The antibody in Surrey was only found in new tests that used M or N gene products as targets and the assay generated some cross reactivity with OC43. The Surrey samples had OC43 antibodies because the patients had symptoms of a cold (and an OC43 infection). Moreover, the more traditional antibody tests did not detect cross reacting antibodies and registered the Surrey samples as negatives.
In view of those results, I doubt that the Guangzhou and Beijing labs are using antibody tests that cross react with coronaviruses that cause colds (OC43 or 299E). Moreover the patient did not have cold symptoms, he had classical SARS symptoms, including pneumonia.
Thus, I think that the lab data has met the criteria for confirmed SARS many times over, but the sequence data has raised the possibility of contamination.
I suspect that instead of contamination, the samples are positive for SARS CoV RNA and antibody because the patient has had a reactivation of the SARS CoV infection he had last March.
Re-activation of SARS CoV has many medical as well as social and economic implications, which could loom large if this is re-activation and is not an isolated case (and I think that it is far too early in SARS season to classify this case as atypical. |
