One of the biggest limitations to knowing the depth of the impact of COVID-19 and enable our recovery is the lack of testing and the ability to apply testing at large scales. Without testing, we are still unaware who has been infected and the extent that the overall population could potentially have some immunity. Given the limitations of testing, companies and researchers are using different proxies to better understand the extent of infections.
One method has been to test human waste in sewage facilities. The idea is that human excrement has traces of the virus when it leave people’s bodies. The Ribonucleic acid (RNA) of the virus soon begins to break down but it leaves a significant trace to indicate the virus was present. Measuring the rate or presence of COVID-19 RNA in human waste provides a proxy for the rate of overall population infection. Furthermore, it provides potentially more accurate localized data for communities, as many urban regions have a limited number of sewage facilities, meaning sewage facilities act similarly to a mass testing center. Additionally, the samples give a snap-shot of the current situation as sewage is cycled quickly through processing plants, meaning that is also a form of real-time testing. The testing of sewage has been applied in the United States, such as by the company Biobot, and European scientists to some success, as health official can get a sense of the rate in which the virus is present in different communities. However, testing of this type is not widespread and some have called for more use of such testing given the limitations of individual testing.
One group of scientists in the Swiss Federal Laboratories for Materials Science and Technology (Empa) and ZTH Zurich in Switzerland is using the air itself as a way to test for COVID-19. Using sensors that are crafted based on the RNA signature of COVID-19, air that contains elements of the virus could bind with the uniquely created sensors to detect the presence of the virus in an area. The technology uses a sensor called localized surface plasmon resonance which contains nanostructures that become sensitized when contacting particles that contains the RNA of the virus, where the plasmonic near-field changes within the nanostructures, informing optical sensors of the presence of the virus. This technology had been used to detect pollutants in areas but researchers were able to manipulate the sensors to be sensitive to the RNA signals of the virus. The sensors also use a thermal effect, something called plasmonic photothermal, which results from binding of the RNA strands with a complimentary strand. In other words, when the strands of the sensor match with strands in an air sample, this happens at certain binding temperatures which can be detectable. This provides a secondary, complementary way to detect the presence of the virus, which could act as a validation of the air test. For now, this method has not been deployed but is being prepared to be used in Switzerland in the near future.
Global travel is of course what led to COVID-19 becoming a pandemic. To prevent a large second wave of the virus, airports around the world are beginning to use thermal cameras to detect passengers who may have been infected as they arrive or go through airports. While this is a relatively low cost way for mass screening of passengers, as thermal imaging can be placed at a safe distance from travelers, detect body temperatures, and be applied as people walk through an airport, there are limitations with such testing. The main problem is the incubation period of COVID-19 can be quite long, up to 14 days, meaning that people do not show temperature symptoms until long after they have the virus. Thus, people could go through areas without being detected but still carry the virus and infect others. Earlier outbreaks, such as SARS, also showed that thermal imaging can help but still be limited in detecting many cases. While thermal and infrared cameras are known to be limited in detecting infected individuals, it represents one of the few ways to conduct rapid mass testing, particularly at travel nodes. Work places such as Amazon, airports, and the military have currently adopted such technologies for their workplaces and sites.
We face an unprecedented challenge of monitoring COVID-19, particularly at large scales where mass testing needs to be done rapidly. However, some new technologies are potentially showing promise, even if they are somewhat unconventional. Testing our sewage could be effective for gaining a sense of the presence of COVID-19 in a given area, as it represents a form of mass sampling that is easy to obtain in a limited time frame. Sensors that bind to the RNA structure of COVID-19 could be another form of mass testing but has yet to be rolled out, as it also needs to be developed so it can test the air over a wide area. Such testing could also deploy genetic binding as a second test. For now, thermal cameras are perhaps the best known form of rapid mass testing, but they are limited as they can only be effective when someone is showing clear temperature symptoms. Given the importance of finding ways to conduct mass testing, we likely see even more new technologies developed in the coming weeks.
 For more on COVID-19 testing of sewage and human waste, see: https://www.health.com/condition/infectious-diseases/coronavirus/coronavirus-sewage-testing and https://medium.com/@biobotanalytics/how-many-people-are-infected-with-covid-19-e7e8c6195d6b
 For more on using the air to test for COVID-19, see: https://www.empa.ch/web/s604/coronatest
 For more on the limitations and use of thermal imaging in detecting COVID-19, see: https://www.wired.com/story/infrared-cameras-spot-fever-not-slow-covid-19/
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