Infectolab - SARS-CoV-2

How Do People Know They’ve Been Exposed To SARS-CoV-2 Coronavirus If They’re Asymptomatic?

The COVID-19 (coronavirus) pandemic spanning the globe picked up speed extremely quickly. In just a few short months, the virus spread from its suspected origin China to over 185 countries in the world. COVID-19 is a part of the coronavirus family, which includes both SARS (Severe Acute Respiratory Syndrome) and MERS (Middle Eastern Respiratory Syndrome). However, COVID-19 has spread exponentially in comparison to both SARS and MERS, both of which had worldwide cases less than 10,000.

With its rapid spread, medical researchers have had a hard time pinpointing specific details surrounding the virus. What we do know is that it has an incubation period of anywhere from one to 14 days, with the average number of people exhibiting symptoms by day five. Because of the virus’ spiked, sticky exterior, it latches on to healthy cells with ease. The most common area the virus establishes itself is the lungs, and it does so by entering ACE2 receptors. But how do people know if they’ve been exposed to SARS-CoV-2 coronavirus if they’re asymptomatic?

COVID-19 vs. SARS and MERS

The reason for the rapid spread of COVID-19 is likely due to the high contagion rate (2–2.5) and ease of travel across global populations. COVID-19 also has a higher likelihood of being transferred through community transmission than SARS and MERS because it is highly contagious earlier on, often prior to the onset of symptoms. The viral load of COVID-19 is also present in the nose and throat, making transmission through air droplets easier.

One study surrounding the virality of COVID-19 came to the conclusion that although both SARS and COVID-19 attack the body using the same host cell, the success with which they do so slightly differs. In the case of COVID-19, the virus protein involved in binding to receptors (thus causing infection) does so with higher affinity. This means that although the two viruses are quite similar, COVID-19 is better at infiltrating the body, which could be the reason it has spread at a significantly higher rate than SARS.

How to tell you have CV19

For many people who have contracted COVID-19, the most common symptoms will appear around 1–14 days after infection and include a dry cough, fever, and shortness of breath. Other less common symptoms include runny nose, headache, sore throat, gastrointestinal issues such as nausea or diarrhea, and body aches. These symptoms range from mild to severe, but the majority of cases will not require hospitalization.

Some people who contract the illness may not show any symptoms at all, or experience symptoms so mild they may not even know they have been infected. These people will not be tested, nor will they feel the need to seek any medical treatment, so it is hard to pinpoint exact numbers of those infected across the globe.

Infectolab - hospital
Image by Sharon McCutcheon on Unsplash: The most severe cases of COVID-19 lead to hospitalization, sometimes requiring breathing assistance.

How asymptomatic people know they have COVID-19

Without showing symptoms and getting tested, there is no true way to know whether one is infected with COVID-19. In efforts to track the spread of the virus and curb new cases, countries such as Iceland implemented widespread testing. One study done on residents of the Nordic country found that around 50% of cases that tested positive were showing no signs or symptoms at all, and as many as 33% of all positive cases in Southern China were asymptomatic as well.

This skew of the true infection numbers impacts the overall data collected by epidemiologists trying to curb the rate of infection and develop a vaccine. In countries where testing is less available, the data could be even more negatively affected; in areas with higher populations but less testing, the numbers could be severely skewed.

How can you track asymptomatic people with coronavirus?

In terms of long-term treatment and spread avoidance, the need for widespread testing has never been so important. Tracing the steps of the highly contagious virus needs is vital so epidemiologists can import accurate data on how fast it is spreading, how many people it has affected, and the percentages of those who suffer severe complications.

These data points will be used in the battle against future outbreaks, and without the proper information, the onus falls on guesstimates. To track and report proper numbers, widespread testing of all areas that have seen numbers of positive cases rise would need to be performed.

How does a SARS-CoV-2 serology test work?

Testing for COVID-19 has been difficult. In the past few months, several tests have been developed specifically to detect the virus’ antibodies to help determine those who have contracted the illness. A serology test, specifically InfectoLab’s ELISA test, works by detecting a specific spike protein. The S1 domain of the spike protein can detect antigens in the bloodstream that can confirm infection in those who have no exhibited any symptoms at all.

Using IgA (antibodies), the serology test is more effective at detecting the virus because of the high affinity in the mucosal areas of the body. This means that IgAs tend to read better on tests. The serology test will also look for certain antibodies that could help lead further treatment using blood plasma from those who became infected with the virus and fought it off.

Infectolab - coronavirus map
Image by Brian McGowan on Unsplash: Testing blood for antibodies could lead to further treatment of COVID-19. 

PCR tests vs. serology tests

A PCR (polymerise chain reaction) test works by detecting the virus’s genetic material in the bloodstream of the patient. The use of PCR tests helped detect the flu in patients in prior years, but when it comes to a global health epidemic, these tests don’t quite stack up.

Aside from the limited supply of these PCR tests, they can also return false negative results in about 20% of cases. A false negative test can lead to further infection and spread of the virus if those tested believe they are COVID-free and continue as normal in their day-to-day lives. A PCR test can also miss the virus if the RNA is no longer present in the body because the patient has recovered.

Featured image by Fusion Medical Animation on Unsplash

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