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INTRODUCTION:
A Chinese woman and her husband living in Hong Kong went to visit to her family in the Guangdong Province, China. They stayed at a hotel for one night, then returned to Hong Kong where they live with their two sons, daughter-in-law, and 5-month-old grandson. The woman soon came down with flu-like symptoms including sore throat, cough, and swollen glands. Her family physician diagnosed her as having pneumonia, put her on antibiotics and sent her home. Three days later, her symptoms worsened and she died.
The woman’s son came down with fever two days later. He developed a cough, chest pains and indigestion. He was diagnosed with community-acquired pneumonia and admitted into the hospital, where he was given intravenous, broad-spectrum antibiotics. Six days later, he died of multiple organ dysfunction.
Within days, all adult members of their household, as well as immediate family members not in the household, came down with flu-like symptoms. In addition, the 37-year-old physician who had treated the son developed a fever, cough, and severe headache. Another patient, who had been in the waiting room with the woman and her husband, came down with a fever and malaise. The list goes on.
What started as a local outbreak of pneumonia quickly spread throughout Southeast Asia. First, the Chinese Ministry of Health reported 305 cases of acute respiratory syndrome. Then a traveler to Hanoi spread the disease to health care workers in Vietnam. A month later, the disease appeared in Hong Kong, where hundreds became sick. This disease seems to spread casually through hotel lobbies, airplanes and hospital waiting rooms. Of those infected, about 10% die, especially the elderly. There seems to be no end in site to the spread of this unidentified, fatal pathogen.
INSTRUCTIONS: We have developed a series of questions for you to answer as you go through this case study. Download and print a copy of the WORKSHEET.
RESOURCES:
Background Information:
Methods:
Pathogen Library:
THE PROBLEM:
As an epidemiologist for the World Health Organization, you are called upon to help identify this pathogen so it can be controlled before hundreds more die. First, you must learn all you can about infectious causes of pneumonia and flu. Then you will analyze test results until you find the culprit.
RESULTS I:
RESULTS I:
Local physicians had collected sputum (deep mucus) specimens from some of the patients who died. You had Gram stains done on all the sputum samples. Below are images that show the results of those Gram stains, as well as results from the sputum of a healthy person.
Be sure to compare these images with the Gram stain images of bacterial pathogens in the Bacteria Library. Note the size, morphology and color of the cells you see– which are bacteria and which are human cells?
RESULTS II:
RESULTS II:
Having looked at the Gram stain results, you decide you need more information. You order direct fluorescent antibody tests from the sputum samples to look for some common respiratory viruses that may be growing in host cells. Fluorescently -labelled antibodies specific to each virus were added to sputum samples to look for the presence (or absence!) of each particular virus.
More information about the Direct Fluorescent Antibody assay is available in the methods section.
UPDATE: VIRUS ISOLATED!!
UPDATE: VIRUS ISOLATED!!
You now want to see if you can isolate viruses from the sputum samples. Because there may be only a few pathogens (particularly viruses) in a given sample, you have to grow the virus in tissue culture cells before examining the sample with electron microscopy. You inoculate 3 different mammalian cell lines with sputum samples from patients. Any sign of cell damage in the tissue culture cells is an indication that there is a virus replicating in those tissue culture cells. You then prepare those samples that show tissue damage for electron microscopy.
Finally, after weeks of intense work, you are able to purify some viruses in cell culture lines and get electron micrograph images of some viruses.
Go to the Virus Library to view EM images of some common viruses and compare them to what you see below.
CONCLUSION:
Time is running out– we need your recommendation now!
Consider all the results that were presented in this case.
What did each set of results tell you? Do all the results agree?
What do you think is causing the outbreak? What conclusion is best supported by the results?
Do you think these are conclusive results? What tests would you recommend next to conclusively prove the etiological agent of this outbreak?
Your answers should be thoughtful and well-organized, and it must incorporate the results you obtained in this case study. That is, use the information from your results and in the references to support your final conclusion.
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