Background: SARS is caused by infection with a coronavirus called SARS-associated coronavirus (SARS-CoV-1 or SARS-CoV). The disease was first reported in Asia in 2003, and SARS-CoV was unrecognized prior to this outbreak. It infected over 8,000 people and killed over 700. SARS-CoV is spread person-to-person via respiratory droplets produced when a person coughs or sneezes. Symptoms include high fever, headache, and body aches, with a rapid progression to pneumonia. Laboratory diagnosis is made using RT-PCR to detect the presence of SARS-CoV genetic material in respiratory samples, or the testing the blood for antibodies to SARS-CoV by ELISA. Antibodies may not be detectable until a week or longer after infection, so RT-PCR is preferred early in an infection. (Since the virus genetic material is RNA, reverse transcription (RT) is used to copy the RNA into cDNA for the PCR test). There is no specific treatment for SARS, nor is there a vaccine for SARS-CoV.
SARS-Cov-1 is closely related to SARS-Cov-2 (Severe Acute Respiratory Syndrome Coronavirus 2), the strain that caused the COVID-19 pandemic (Coronovirus Disease 2019). There have been no new cases of SARS since April 2004, but COVID-19 is still a major pandemic as of 2021.
Note: An ELISA test is considered positive if the color production (absorbance) for a sample is at least twice the negative control value. PCR results are recorded as viral load values, i.e. how many copies of the virus were detected.
Case A. Dr. Smith, a physician at a hospital in Hamilton, Ontario observed four cases of what appeared to be a viral pneumonia within the last week. The symptoms resemble those associated with SARS. The patients all had high fevers and difficulty breathing, and their x-rays showed signs of pneumonia. Bacterial cultures were negative. None of the patients reported traveling out of the country recently. The first patient who was admitted seems to be recovering, but the second patient has taken a turn for the worse, and may not last the night. Dr. Smith remembers very well the SARS outbreak in Toronto, just one hour north of Hamilton. Most of the more than 300 people infected were exposed to the virus while in a Toronto hospital, as a patient or visitor. Some of the casualties were health care workers who contracted the virus while treating patients. He and the rest of the clinical staff have been taking every possible precaution, and the patients are in an isolation ward in the hospital. Dr. Smith is anxiously awaiting the results of the laboratory tests.
Procedure: To analyze this case, two types of tests are necessary. Run an ELISA test on blood samples to test for the presence of virus proteins. Also, run RT-PCR on the samples to try to detect the virus genetic material; DNA from these samples is used in the PCR test.
Samples for ELISA
- Protein: Positive control for SARS-CoV
- Protein: Negative control
- Protein: Patient 1 (57-year-old male)
- Protein: Patient 2 (51-year old female, wife of patient 1)
- Protein: Patient 3 (43-year-old female)
- Protein: Patient 4 (69-year old male)
- Antibody for SARS-Cov
Samples for 96-well PCR
- DNA: Positive control for SARS-CoV
- DNA: Negative control
- DNA: Patient 1 (57-year-old male)
- DNA: Patient 2 (51-year old female, wife of patient 1)
- DNA: Patient 3 (43-year-old female)
- DNA: Patient 4 (69-year old male)
- Primers for SARS-Cov
- Are any of the patients infected with the SARS coronavirus?
- If so, what should be done to treat them?
- What are the risks of spreading the virus in a hospital setting?
- Where/how might these patients have been exposed to the virus?
- If any of the patients are negative for SARS CoV, what else could be causing their symptoms?
- How risky is it for the health care workers who treat SARS patients?
Case B. Shi Jiao-hui has lived in the New York City almost all of this life. His parents moved there when he was two years old. He is a U.S. citizen and considers himself a New Yorker, but the rest of his extended family still lives in Guangdong province in China. Finally, at age 30, he and his wife, Ming, and their son and daughter traveled to China to visit his relatives and see his homeland. Their 3-week trip took them through Hong Kong and several cities in China, and they spent the last week with relatives near the city of Guangzhou. Unfortunately, Ming was very sick most of that week. She had a high fever and difficulty breathing. She was taken to a hospital in Guangzhou where she was treated for pneumonia. She recovered enough to fly back home and is doing fine now. However, Jiao felt ill soon after returning home and now has the same symptoms as Ming. When he goes to the clinic the physician is alarmed by the description of the symptoms and the fact that the family had recently visited the area where SARS was first reported. He recommends that Jiao be tested for SARS coronavirus infection and collects a throat swab. He also recommends that the two children be brought in for testing. In the meantime, Jiao is hospitalized and placed in an isolation ward.
First procedure: To analyze this case, run an ELISA on the proteins in throat swab samples from Jiao and the two children, as well as a PCR test on cDNA isolated from the sample. For this test, use autoload for ELISA and select the option ‘Load same antibody, different proteins’.
Samples for ELISA – testing proteins from family members for antibody to SARS-Cov
- Protein: Positive control for SARS-CoV
- Protein: Negative control
- Protein: Jiao
- Protein: Son
- Protein: Daughter
- Antibody for SARS Cov
Samples for 96-well PCR – testing proteins from family members for antibody to SARS-Cov
- DNA: Positive control for SARS-CoV
- DNA: Negative control
- DNA: Jiao
- DNA: Son
- DNA: Daughter
- Primers for SARS Cov
Second procedure: Test Ming’s blood for antibodies to SARS-CoV proteins. For this test, use autoload for ELISA and select ‘Load same protein, different antibodies’.
Sample for ELISA – testing Ming’s blood for antibodies to SARS-Cov protein.
- Protein: Positive control for SARS-CoV
- Antibody: Ming
- Antibody: Negative control
- Antibody for SARS Cov
- Is Jiao infected with SARS-CoV?
- Do either of the children appear to be infected?
- What should the recommended treatment be?
- Was the physician right to place Jiao in isolation?
- Was Ming infected with SARS-CoV while in China? If so, why didn’t the doctors there tell her?
- What should be done to minimize the risk that Jiao will infect anyone else?