SARS nearly escapes from lab via researcher
Poor procedures, training needs cited
While epidemiologists await a possible natural resurgence of severe acute respiratory syndrome (SARS), a cautionary tale from Singa-pore underscores that another global outbreak of SARS could be triggered by a laboratory accident.
Inappropriate laboratory procedures and a cross-contamination of West Nile virus samples with SARS coronavirus in the laboratory led to the infection of a doctoral student in a Singapore lab, investigators have concluded.1
No evidence could be found of any other source of infection. Genetic sequencing supports the conclusion, as the lab strain and the worker’s strain were closely related.
After a rigorous investigation, investigators found no evidence of secondary transmission to the lab worker’s contacts and caregivers. Still, the case reinforces that labs can be a source of infection, threatening both laboratorians and the surrounding community.
The committee identified numerous problems with the lab, and concluded it only should be allowed to open after it has been re-audited and issues related to the structure, the use of the BSL-3 laboratory, training of staff, and a risk assessment of work have been carried out to a level acceptable by a safety committee.
Training needs to be thorough, competency-based, and include a significant period of direct supervision, investigators recommended.
"Training on the responses to emergency situations is critical, because failure to react correctly can result in an incident moving from manageable to an uncontrollable situation," the investigators concluded.
The worker in the SARS case is a 27-year-old man in his third year of a doctoral program in microbiology at the National University of Singapore (NUS).
On the evening of Aug. 26, he developed fever and muscle pain. Between Aug. 27 and Sept. 3, the patient visited his general practitioner, Singapore General Hospital (SGH) emergency department, and a Chinese physician. On Sept. 3, the patient had persistent fever and returned to SGH; at this time, he was admitted. Interviews with the patient revealed that the patient was in a laboratory where SARS coronavirus work was being conducted, and several specimens were taken for testing.
Investigators concluded that the patient acquired the infection through laboratory contamination based on the following evidence:
1. He worked in BSL-3 laboratory 3.5 days before his illness onset. This is consistent with the expected incubation period for SARS. Although the patient reported only working on West Nile virus, the laboratory was doing live SARS work around the same time.
2. Poor record keeping makes it difficult to ascertain if there was live SARS virus in the BSL-3 laboratory on the day of his visit, but it is known it was there two days before.
3. Procedures for laboratory safety differed widely between laboratory personnel and were not always appropriate.
4. Testing of the frozen specimen that patient worked with on Aug. 23 was positive by RT-PCR for the SARS coronavirus and West Nile virus, suggesting contamination.
5. The lab only works on one strain of the SARS coronavirus, so the laboratory strain and patient strain were sequenced for comparison. Approximately 91% of the genome was sequenced from the patient and found to be most closely related to the sequence of the laboratory strain. Minor differences observed likely are the results of the natural mutation rate for the virus.
1. Singapore Ministry of Health. Biosafety and SARS Incident in Singapore September 2003: Report of the Review Panel on New SARS Case and Biosafety 2003: 1-31.