Moment Epidemiology Update | Understanding Testing
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It’s difficult to sift through the constantly developing news about the novel coronavirus. Much of it is confusing and, unfortunately, some of it is false. We reached out to an epidemiologist to give us clear facts about COVID-19 and some guidance in these uncertain times. Send questions to be answered in this ongoing series to email@example.com
There is a broad scientific consensus that widespread testing is the best way to understand the scope of the coronavirus pandemic. Testing people with and without symptoms can help scientists better understand how the virus behaves. This behavior is what epidemiologists are currently racing to comprehend.
We have a limited understanding of testing capacity in the United States because on March 2 the U.S. government removed all data on the number of tests being performed from their website. We can, however, look to other countries for instruction and guidance. South Korea, for example, has conducted extensive testing. It has tested more than 270,000 people or approximately 5,000 tests per one million inhabitants—more than any other country except tiny Bahrain. For context, the U.S. would have to test approximately 1.62 million people to match South Korea’s test rate.
After South Korea identifies a positive COVID-19 case, based on extensive population testing, it completely isolates the positive patient. Based on this strategy, South Korea has been more successful than many other comparable countries in containing the COVID-19 epidemic. But how exactly have South Korea, and other countries, been testing for COVID-19?
At present, scientists have the capability to test suspected patients for current COVID-19 infections with a test called Real Time Polymerase Chain Reaction (PCR). For example, Patient A goes to her local hospital to get tested for COVID-19. A medical professional uses what is essentially a very long Q-tip to swab the back of Patient A’s nasal cavity for a very small sample. Once they have a sample, it is sent to a lab where scientists use the PCR method to make millions of copies of the sample from the back of Patient A’s nose in order to study it in detail. Scientists are looking for a specific COVID-19 RNA sequence. If they find it, that means Patient A has tested positive.
In the United States, there have been a number of delays in using the PCR test. Early delays occurred when the Centers for Disease Control decided not to use the same viral gene segment—that strand of identifiable RNA of COVID-19 the testers are looking for—as the World Health Organization. Later, there were issues with the chemicals sent to the State Health Departments to run the PCR process.
Additional delays have been caused by laws and regulations requiring the U.S. Food and Drug Administration (FDA) to review and approve any commercial diagnostic test. Regulatory approval is critical since it is important that the PCR test accurately identify those truly infected with the virus in order for epidemiologists to understand the scope of the virus and for an isolation strategy, similar to that deployed in South Korea, to be effective. Public and private laboratories are now able to run PCR tests to diagnose the virus. However, there is still a delay in testing because chemicals are in short supply, as are other materials required for the tests such as plastic vials and swabs.
A second type of diagnostic test has recently been developed and approved to look for evidence of past infection with COVID-19, according to the Wall Street Journal. Evidence of a past infection can be seen by measuring the antibody levels a patient’s body produces in the fight against the coronavirus active in that patient’s blood sample. The test, which just received FDA approval, should be available this week, according to Abbott Laboratories.
Accurate testing for past infection with COVID-19 will also be extremely useful to screen health-care workers and identify those who are already immune so that they can be deployed to care for infected patients, thereby minimizing the risk of viral spread to colleagues and other patients. Such a test will also allow us to understand the true magnitude of asymptomatic carriers in the population—people who have or had COVID-19 without symptoms—and the true mortality rate. Finally, the test will allow society to begin identifying people who are immune to COVID-19 so that they can return to their normal lives. A home test of antibodies is also being developed which will be useful for self-diagnosis of existing immunity.
As the scientific community works to develop and deploy these tests we all can help by social distancing, washing our hands frequently and thoroughly, and avoiding touching our faces. This will allow scientists more time to develop and deploy these new detection techniques.