Written by JobSiteCare
June 15, 2020
Two weeks ago, the CDC changed its messaging on the major causes of COVID-19 infections. The intent was not to change the assessment of the science but to clarify the importance of various methods of transmission. Unfortunately, the public took this as a major change in the way we should address COVID-19 transmission. The new messaging highlighted the importance of person-to-person airborne transmission of COVID-19 and de-emphasized the importance of infection via surfaces. Many began to question the importance of hand sanitizing and frequent cleaning of surfaces.
This was not the intention of the revised messaging. There is no question that surface transmission plays a role. It is still important to pay attention to the precautions we have all been taking to avoid contracting the virus from the environment.
There is a new understanding of the role of small particles in the air. The small particles are projected not only from coughs and sneezes but also from talking. These particles remain suspended in the air for at least a few minutes before landing on surfaces. The human body is very effective at handling a small number of these particles. However, if you spend too much time in an area with a low density of these infectious particles, it may be enough to lead to an infection.
These findings emphasize the importance of both time and distance in reducing the risk of infection. It has solidified the CDC and WHO guidance that risk does not substantially increase until you reach a threshold of being within 6 feet of an infected person for more than 15 minutes. Logically, this also means that closer exposure for a shorter amount of time, or longer distance for a longer amount of time may also increase risk. The 6 feet (or 2 m) for greater than 15 minutes is still an effective guideline for high-risk contact. Importantly, this guidance does not address masks. There is good evidence that a mask worn by a person who is infected decreases the number of particles that are expelled on an ongoing basis. This does provide a scientific basis for continued attention to masks in public.
Late last week, a senior official of the WHO stated that there is little evidence that asymptomatic spread significantly contributes to the epidemic. She also stated that there was new unreleased data that supported this contention. If true, this would have made a major difference in the way we address this epidemic. For most epidemics, including influenza, people cannot spread an infection until they are ill. At that point, they take themselves out of the population until they recover. This means that monitoring for symptoms and ensuring people who are ill stay excluded from schools and workplaces can effectively control an outbreak.
Over the weekend and early this week however, the WHO put out significant clarifications of the doctor’s statement. The WHO said that what she meant to say was that people who are asymptomatic appear to have a minor role in the spread of infection because their relative number is few. And for whatever reason, these people do not project infectious virus at a concentration as high as people who do become ill.
Another major component of the epidemic are those who do not have symptoms because they are presymptomatic, or about to develop symptoms. Unlike most other viral infections, during the 24 to 48 hours before developing any of the symptoms that are associated with COVID-19, most people begin to project infectious particles without knowing it. This is the reason that we are all wearing masks in public. Nobody knows who has been infected, or who is already capable of infecting others. Masks can significantly decrease the projection of viral particles, especially before someone develops a cough or sneezing that may be associated with the early symptoms of the virus.
Several companies are coming to market with saliva-based testing as an alternative to nasal swabs. This type of testing can be performed, under supervision, by the person who is being tested. This makes the testing process much easier and safer for everyone. This test, however, still requires obtaining the test equipment, performing the test, and then shipping the test to a laboratory. The results of these tests are typically received in 2 to 3 days. So far, the accuracy of the test appears to be comparable to the large laboratory-based tests. This test addresses two characteristics that we are looking for to increase the utility of testing. For the sake of efficiency and effectiveness, tests need to be fast, accurate, and, easy to perform. This test addresses the last two but it is still far from the immediate test that we will need to make for testing to play a major role in the “test and trace” strategy that public health authorities are looking for.