The number of positive coronavirus (COVID-19) cases has risen exponentially since the virus first appeared in late 2019. For many, symptoms of the virus have included fever, trouble breathing and a dry cough. For others, though – some who may not have even thought to get tested – the virus can be asymptomatic.
When this occurs, no outward symptoms are present, and the person who contracted the virus can act as a carrier or host without ever knowing that they had it in the first place. These asymptomatic cases have been deemed less dangerous than those who show symptoms, because they are less likely to expel air droplets containing the virus into public areas. But people without symptoms are also less likely to adhere to certain safety measures if they believe they are free of COVID-19. This is detrimental to the fight against the spread of the virus – but if a great number of people are showing no symptoms at all, how can the illness be stopped?
Is there asymptomatic transmission of the coronavirus disease?
One of the most important ways researchers and medical organisations can slow the spread of coronavirus is by tracking how it is spreading in communities, at what speed it is moving, and how many are suffering from severe complications. This level of tracking is the only way to gather enough data in the fight against the virus. The process of developing treatment also relies heavily on tracking, because those who have recovered from the illness or have been infected without suffering from symptoms could be key in developing a vaccine.
In another way, tracing the spread will also help organisations to create more accurate projections when it comes to how far and how devastating the effects of the virus will be in any given area. This will depend entirely on the rate of spread in an area, the number of patients who suffer from severe complications, and the level of recovery. These projections are important because researchers will be able to get out ahead of the virus easier when given a better idea of how it is moving through populations.
The problem with tracking the spread of COVID-19 lies in the amount of transmission that occurs under the radar because of those who have not yet been tested (usually because they lacked the typical or serious symptoms needed to require or even qualify for testing). When a person is infected with the virus but doesn’t show symptoms, they can be just as contagious as those who do. The only difference is that they may not take the same safety measures as others – which, in theory, could lead to a worsened spread of the virus through a community.
How do you track community spread of coronavirus?
To track COVID-19 throughout communities, it’s important to monitor where positive cases arose and how fast it spread throughout the population. In places like Italy, the rate of spread was quick and led to many deaths. In other places, such as Mongolia, there were no reported cases of local transmission. Mongolia’s small number of cases was acquired through imports of the virus only.
This differentiation can provide insight on how to track the community spread in other areas. Other tactics that have been used around the world include surveillance – that is, combining data sources from confirmed cases, lab reports and other surveillance systems, which when put together create a picture of where the disease may have started and how it was passed around locally. Other measures, such as widespread quarantines, have taken place to help limit person-to-person contact and narrow down where the worst outbreaks are occurring.
What proportion of people are asymptomatic with COVID-19?
According to the CDC, around 25% of those who have contracted COVID-19 will be asymptomatic, although studies conducted in China and Iceland have put the number as high as 50%. Considering the sheer numbers of those already infected, the numbers of undocumented cases could be even higher. Due to the low availability of testing in areas where the virus is rampant, not all those who have contracted the illness are able to get tested.
Furthermore, because of the number of people who are infected but not showing symptoms, community transmission of the virus could in part be due to the fact that those who aren’t confirmed cases can still transmit it and are more likely to break self-isolation precautions. Containment of the virus also relies heavily on tracking the spread and tallying the numbers of the infected, but with those who are asymptomatic, that cannot be achieved.
Ways to track asymptomatic people with SARS-CoV-2
The only true way to track the real numbers of those infected with COVID-19 is through testing. The tests that have been available so far have largely only been conducted on those suffering serious complications or showing obvious symptoms, but a new serology test that has been developed may be able to step in and bridge the gap between the current numbers of confirmed cases and the true total around the world.
The antigen used in the BCA-lab serology test is the S1 domain of a spike protein for SARS-CoV-2. This is the most immunogenic and specific protein used by the SARS-CoV-2 virus to infect cells. By using this protein we massively reduce the risk of a false-positive result due to cross-reactivities of other coronaviruses. Our test also searches for the presence of IgA antibodies (an antibody that can be found in mucosal surfaces) over IgM antibodies. As IgA is more specific to coronavirus antigens than IgM, we are able to increase our test sensitivity to a minimum of 85% accuracy (as opposed to the maximum 25% accuracy achieved in other SARS-CoV-2 serology tests).
Researchers hope that this new test will be available to help confirm cases in those who are ill as well as effectively detect asymptomatic patients in an effort to help slow the spread of the virus. It’s also hoped that the new testing will lead to a possible treatment for those who are ill, and possibly even provide temporary immunity for medical staff working on the frontlines by giving them a dose of hyper-immune blood plasma (donated by previously infected, now recovered patients) containing the specific antibodies needed to fight off a COVID-19 infection.