Two kinds of tests are used to determine COVID-19 infection. One, the PCR test (polymerase chain reaction test), can be done with a throat swab and determines if you have the infection now. This test is used for those concerned if they have the virus because of symptoms.
The second test is the antibody test and has growing interest as it can determine if you have been infected with the virus and fought off the disease. Both tests have many false positives, and recent exposure, particularly with the antibody test, may not trigger a positive for one to three weeks.
The antibody test is a better test to determine the infectivity rate in the community. Most people seeking a test do so because they have symptoms (PCR) but is not helpful in determining how many in the community have been exposed.
The antibody test can be given to a sampled population with or without illness and can give a more accurate picture of the community spread. Not everyone exposed will show signs of the disease yet those same individuals can spread the illness with or without symptoms.
The United States has a population of 331 million people, testing everyone is not practical in a short period of time. Random sampling of a representative population regionally can give us valid information as to how prevalent the virus is in the community. We do such random sampling every year with the annual “Flu” bug. Knowing the infected population numbers with or without illness is critical information.
Less than three percent of the population has been tested to date. The testing has mainly been on demand testing (PCR). The sample is biased as many who carry the virus do not seek testing either because their symptoms are minor or have no illness. Some Public Health officials have suggested that the infection rate may be 20 to 30 times more prevalent than reported. That makes it very difficult to clearly understand the danger of the virus. For example, death rates could be much lower than suggested by the current data.
It is known that the elderly and those with chronic medical problems are at the highest risk to develop serious disease or succumb to the illness. What we don’t know is how many are carrying the virus which would then give us an accurate picture of individual risk. Such information is crucial in determining a community getting back to normal activity, work, shopping and recreation.
The lack of this knowledge as we reopen our communities would suggest that individual caution used. Continue to use a mask, continue social distancing and understand your risk as determined by your age or chronic medical conditions. A wise approach could save your life and those close to you. Stay safe.
Dr. Marc J. Yacht is the retired director of the Pasco County Health Department.