If you have been to a healthcare facility recently or work in a hospital, chances are you have been screened as soon as you got to that location. Sometimes, you are even screened prior to arrival. The same strategies are being proposed to help us return to our "normal" lives. While this may seem like a beneficial strategy, there is a significant problem with these screening protocols.
First, screening protocols are meant to help separate those sick with a disease versus those that are not sick. A major problem in the case of COVID-19 is that there is a very high prevalence of asymptomatic patients. While this is good in regards to many people doing well who have the infection, this leads to a rather challenging task of screening.
It is still important that we identify these individuals to help avoid the spread of the virus. If we fail to recognize those patients or individuals in the community with the infection we can cause significant spread. However, there are not enough tests at this time for universal testing.
We should talk about some of the evidence that has recently pointed to issues regarding screening protocols and the rate of infection. As an important note for these studies, some of them have not yet been formally peer reviewed. This is becoming commonplace with research surrounding COVID-19, but it is important that we acknowledge this for transparency and remembering to be more skeptical with these results. However, these studies carry similar results and through various methods are being openly critiqued such as on medRxiv.
The first is published in the New England Journal of Medicine (NEJM) regarding a cohort of pregnant patients that delivered at two New York hospitals. They were all screened on admission for symptoms. Out of the 210 women, 33 tested positive for SARS-CoV-2 (the virus that causes COVID-19), but only 4 had symptoms (87.9% asymptomatic). The overall prevalence may be higher simply by its geographic region, but we must also remember there are serious concerns with false negative results of these tests.
A very different patient population also has a similar problem. A homeless shelter in Boston tested 408 individuals for which 147 tested positive for the virus. This time, 121 of the 147 (82.3%) were without cough, shortness of breath, diarrhea, or fever. The concern is that in this shelter, there is risk for spread very quickly and often people in such shelters are at risk for a number of reasons including their lack of insurance, comorbidities, and close proximity.
Over in Iceland, people have been tested both by targeted and open population. Another NEJM study demonstrates their results. The targeted population focused on those at high risk including those that were symptomatic, had recently traveled to high-risk countries, or had contact with someone infected. In the next segment, they tested based on an open invitation. Finally, they tested a random part of the population through random invitation. 13.3% of the targeted population tested positive for SARS-CoV-2, 0.8% in the open invitation population, and 0.6% in the random invitation population. While 93% of those in the targeted population who tested positive for SARS-CoV-2 had symptoms only 57% had symptoms in the overall population screening group that tested positive.
Some may argue that they probably have already had the virus. However, a study out of Santa Clara County, California suggests otherwise. In some ways this is convenient as there has been some recent media trying to argue for possible herd immunity in California since many thought they had it. The study suggests otherwise as the unadjusted prevalence of antibodies to SARS-CoV-2 in Santa Clara County was 1.5% and the population-weighted prevalence was 2.8%. While this does point to a higher rate of cases than what has been confirmed by lab testing prior to that point, it heavily implies that those thinking they were infected earlier in the year were most likely not. This also means that currently there is not a large population that has already developed an immune response making a general return to activity safe.
While we strive to return to "normal" we must do so carefully. Many people are asymptomatic and can carry it throughout the rest of the population. The overall prevalence, especially in those that have not been hard hit yet, is not sufficient to provide herd immunity even if it can be accomplished with this disease. Eventually, a "soft reopening" (or something similar) will have to be done, but we must do so cautiously and hopefully in a manner that will not cause further harm.
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