Why Combined COVID Diagnostic Testing and Surface Testing Provides A Stronger Detection and Outbreak Defense

Ten months into the COVID-19 pandemic in the United States, many senior and long-term care communities are still struggling to prevent outbreaks. As of November 30, long-term care communities have suffered over 100,000 fatalities due to COVID-19, despite self-imposed and state mandated strategies being in place. The major culprit: the absence of symptoms until the fourth to fifth day after a person gets infected. The issue with such a long incubation time is that it creates a dangerously deceptive window during which infected people are highly contagious but still socially active. In fact, virtually all the studies looking into  SARS-CoV-2’s viability in COVID-19 patients over time have concluded that the virus is present in high quantities and viable about three whole days before noticeable symptoms. This means that infected staff members continue to come to work in their senior/long-term care facilities or nursing homes for at least three days, while being highly infectious. What’s more, researchers have come to the consensus that patients are the most contagious before symptoms appear. So what can senior care communities do to protect their staff and at-risk residents from the invisible and deadly threat of asymptomatic COVID-19 carriers? 


An effective and proactive COVID-19 surveillance is key to stemming this pandemic

According to Dr. Audrey N. Schuetz, co-director of the Bacteriology Laboratory at the Mayo clinic, situational awareness may be the key to a more efficient pandemic response. In this pandemic, situational awareness is the ability to maintain accurate and real-time data of the current state of the viral threat within a community. “One of the most crucial strategies to maintain situational awareness during a pandemic is having an effective infectious disease surveillance program.”. In long-term care, COVID-19 surveillance takes multiple forms, depending on state mandates, the risk level of a community, their access to tests, and available funding. The main objective of COVID-19 surveillance is to enable rapid detection, isolation, testing and management of infected members to prevent or reduce the spread of the disease. This is especially important in community settings. The most common surveillance strategies require the willing participation of the people being monitored. Self-reported symptoms and temperature checks have become the most widespread surveillance method. Most long-term care communities also conduct diagnostic testing for people who exhibit symptoms or have been exposed to someone who tested positive for COVID-19. Over the past couple of months, long-term care communities have become acutely aware of the risk that asymptomatic COVID-19 carriers present. In July, the Department of Health released a report that concludes that COVID-19 was most likely to be introduced into nursing homes by asymptomatic employees. In light of this risk, senior and long-term care communities, as well as nursing homes, have focused their efforts on detecting asymptomatic carriers. Recognizing the importance of detecting asymptomatic people, some states have made universal diagnostic testing mandatory for those communities. The testing frequency varies from monthly to mandatory daily nasal swabs or saliva sampling for 100% of staff and residents in high risk communities. Senior care leaders report that such high frequency testing has been taking a psychological toll on staff and residents alike and has led hundreds of communities to file for bankruptcy. Yet, despite high-frequency surveillance diagnostic tests, many facilities continue to suffer outbreaks. So what is happening?


Repeated diagnostic tests of asymptomatic people are not recommended by some experts

The issue with using repeated diagnostic testing as the sole surveillance strategy to detect asymptomatic COVID-19 carriers is that it leaves gaps during which the virus spreads rapidly across at-risk communities. The efficacy of such strategy heavily relies on fluctuating conditions such as: 

  • how often the diagnostic tests are performed
  • how well the samples are collected
  • how many people are/accept to be tested, and
  • how fast results are returned

Some experts discourage the use of daily diagnostic tests on asymptomatic people. Four common reasons are often cited:

  1. The low availability of tests, especially rapid COVID tests, means that they should be reserved for people who have been exposed to the virus.
  2. The low sensitivity of rapid tests leads to more false positives when used to routinely test people who are asymptomatic and have not been in contact with infected patients. This, in turn, leads to un-needed depletion of an already dwindling workforce due to staff being put in isolation for weeks following a false-positive diagnostic.
  3. The recurring cost of PCR tests for an entire community (nasal and nasopharyngeal tests) can be prohibitive
  4. Willingness to comply to sampling procedures for diagnostic tests may prove difficult to maintain over time


Anosmia is not a common or early enough symptom to help fill this surveillance gap

Loss of smell is one of the earliest symptoms of COVID-19 and appears before other symptoms in 54% to 65% of cases. For this reason, anosmia has often been mentioned as a good way to detect a COVID-19 infection before other typical symptoms appear. However, a recent study found that anosmia usually appears over four days after the onset of the infection, leaving 1-2 days where patients are likely highly infectious and still working within the facilities. This is where environmental surveillance comes into play.


Environmental viral surveillance bypasses those issues

Looking for coronaviruses on surfaces is not new. This technique has been applied to coronaviruses as early as since 2004, in the wake of the first SARS epidemic. During the COVID-19 pandemic, surface testing has proven to be a powerful tool to detect the presence of infected people within a facility at least five days prior to symptoms (Read the study). This means that using surface testing alerts senior facilities of an infection within the community much earlier than otherwise possible, potentially even before they become highly contagious, effectively preventing an outbreak. The key to nipping outbreaks in the bud lies in the multi-pronged approach to viral surveillance that those communities have adopted. Surface testing plays the role of a sentinel, scanning the environment for a sign of infection. Once the alarm is rung for a specific area/surface, community leaders know exactly who to test based on their access to the surface. Such location-based contact tracing considerably accelerates the identification of infected individuals, limits the number tests needed and reduces the number of staff workers that may need to be isolated.

Early COVID-19 warning window when using loss of smell (upper panel, blue area) or surface testing (lower panel, orange area). Surface testing allows senior care communities to detect asymptomatic COVID-19-positive people at such an early stage that they can identify and isolate those people before they start being highly contagious (lower panel, hashed area). Using anosmia as an early warning strategy also provides early warning, but not before the peak of contagiousness. -Inspired by MIT Medical’s “How long before symptom onset is a person contagious?” 


There are multiple reasons why surface testing has emerged as a crucial tool in the fight against COVID-19.

1) Surface testing is not participatory, essentially relieving senior care staff and residents from the logistics and burden of sample gathering, which are especially difficult on memory care patients.

2) Surface testing has a memory. Detecting SARS-COV-2 on a regularly cleaned surface tells you that someone has recently been shedding the virus within your community. In comparison, diagnostic test results only inform you of the current state of shedding of a particular person at the time of testing. This is problematic because PCR tests and rapid tests alike have resulted in sporadic positive results, where someone tests positive one day, negative the next day, and positive again the following day (study, report). Although such a pattern was previously attributed to reinfections, scientists now believe that it likely due errors in sampling, low test reliability, or even real sporadic virus shedding in certain individuals. Surface testing bypasses those issues, as the virus is detectable on a surface days after contact with a shedding infected person.

3) Surface testing combines high sensitivity and rapid result turnaround. Commonly used diagnostic tests are: 

  • PCR tests, the gold standard used to process swab samples. They have the highest sensitivity and the longest turnaround time (often multiple days, especially when cases surge)
  • saliva tests, which have a lower sensitivity (some report up to 30% false negative) but provide results within minutes. 

“The rapid saliva-based antigen test with the 30 percent false negative rate does a poor job of diagnosing infection […].” say David Paltiel, professor at the Yale School of Public Health and Rochelle P. Walensky, chief of infectious diseases at Massachusetts General Hospital and professor of medicine at Harvard Medical School. 

Enviral Tech’s surface testing uses high sensitivity PCR to process samples and return a gold standard of results within 24 hours of their arrival in our lab. 



Establishing a diagnostic testing program in senior and long-term care settings is important but not sufficient to stem COVID-19 outbreaks. Having an efficient, multi-pronged surveillance strategy that rings the alarm immediately after an infected individual has started shedding the virus is key to protecting seniors against the silent threat of asymptomatic COVID-19 carriers. Surface testing can detect the virus up to 3 days before loss of smell and up to 5 days before respiratory symptoms are known. This valuable advanced notice directs the use of diagnostic tests to rapidly identify infected people among those who had access to the COVID-positive surface. The suspected infected people can then be isolated, potentially even before they become highly contagious, essentially preventing outbreaks.


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