Rapid Detection of the Severe Acute Respiratory Syndrome (SARS) Coronavirus by a Loop-Mediated Isothermal Amplification Assay

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Abstract
Severe acute respiratory syndrome (SARS) is a newly emerging disease that first emerged in Guangdong Province, China in November 2002 (1). The SARS coronavirus (SARS-CoV) was found to be the etiology of the disease (2)(3)(4). Subsequent surveillance studies have indicated that this virus is of animal origin and have suggested that the source of the disease is still circulating in this geographic region (5). Indeed, the potential risk of reemergence of SARS is further highlighted by a recent confirmed SARS case in January 2004 (6). Therefore, the establishment of a rapid SARS diagnostic method is a high priority for control of the disease. Currently, there are two major diagnostic approaches for SARS. Detection of antibodies against SARS-CoV is a sensitive and specific diagnostic approach, but serconversion can be detected only around day 10 of illness (7). In contrast, PCR-based tests have been shown to be useful for early SARS diagnosis (8). Quantitative PCR approaches are a powerful tool for identifying SARS-CoV early after disease onset (4)(9)(10)(11). However, because of the requirements for sophisticated instrumentation and expensive reagents, these rapid molecular tests might not be the method of choice in basic clinical settings in developing countries or in field situations. It is therefore critical to develop simple and economical molecular tests for the above scenarios. The invention of loop-mediated isothermal amplification (LAMP) has opened up a new horizon for molecular diagnosis (12). This method depends on autocycling strand displacement DNA synthesis performed by a Bst DNA polymerase, and a detailed amplification mechanism has been described elsewhere (12). The reaction relies on recognition of the DNA target by six independent sequences, making this kind of assay highly specific. This method is rapid and has a DNA amplification efficiency equivalent to that of …