Testing is important, but still has limitations
Testing, testing and more testing. That is the mantra health experts are telling the American people is the best way to contain the coronavirus pandemic. And they are right, up to a point. But these tests have limitations and those who expect clear-cut advice or a risk-free future are going to be disappointed.
Before understanding coronavirus testing, let’s take a simplified look at how the immune system works. When our bodies are invaded by a virus, the affected cells secrete messenger proteins that signal our white blood cells to attack the virus to prevent further spread. Often this is enough. But then our body comes up with a secondary response. It manufactures specific proteins called antibodies and killer white blood cells that can recognize the invading virus and destroy it if it reinvades. This is called immunity.
Thus, there are two types of tests to check for coronavirus – one identifies the actual virus in a patient; the other identifies the antibodies.
The first type requires a swab of the affected tissue and in the case of coronavirus, it is the back of the throat, reached via the nasopharynx. This tissue is then processed with enzymes that can identify the unique RNA sequence associated with the coronavirus. But this test has been created quickly and generates, according to some estimates, a 30% rate of “false negatives,” meaning that the test is negative even though the patient has coronavirus. The opposite can also occur, where the test is positive even though the patient does not have coronavirus. Naturally, this is called a false positive. This is further complicated by the fact many carriers of the disease have minimal or no symptoms but can spread it to others. Thus, even if we were able to test every American, isolating those positive for the test would not insure the containment of this pandemic.
The second type tests for the antibodies and identifies those who are immune from the disease and may be able to return to the workplace. This test requires a blood sample but can be processed quickly after a simple finger prick. But it has limitations too. Some patients have stronger immune systems than others. Thus, an individual with a weak immune system with a positive test could still become reinfected. Also, an individual may make antibodies quickly while still being a carrier of the disease. Obviously, this person should not be exposed to the general public.
Thus, the best way to prevent spread of this disease is the same as what the Venetians came up with in 1347 to decrease the spread of the Bubonic Plague – a killer of one-third of Europe’s population. It is called quarantine, which comes from the Italian word “quaranta” meaning 40. The leaders of the day empirically determined that this was the optimal time period to sequester a population to diminish the spread of a disease. What is fascinating is that these leaders had no concept of the germ theory but came up with about the same number our leaders are using today.
Forty days is about the time an epidemic will peak, or about the time a population will endure being isolated and unable to make a living before they rebel. Take your pick.
Joe Bentivegna is an ophthalmologist in Rocky Hill.
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