Thursday, 19 March 2020

New Blood Test Could Reveal True Scale of COVID-19 Pandemic

Credit: Felipe Esquivel Reed/Wikimedia Commons

As the world struggles to cope with the expanding COVID-19 pandemic, there are some very basic questions about the virus that remain unanswered. For example, how many people have been infected? A new study from the Icahn School of Medicine in New York City details a test that might help us find out

The coronavirus outbreak has infected about 240,000 people so far, causing almost 10,000 deaths. That puts the death rate at just north of 4 percent, which is extremely high. It’s also concentrated among older populations. So, someone in their 60s or 70s who contracts the virus could have a significant chance of dying. 

The problem with these numbers is that all the math relies upon confirmed and presumptive positive tests. Many nations, including the US, have been caught flat-footed without enough tests to go around. That could be artificially depressing the number of infected people, which inflates the mortality rate. Most public health officials believe COVID-19 is somewhat less deadly than the 4 percent rate would indicate, but we need better testing to know how much lower. A more accurate gauge of mortality can help governments determine how aggressive they need to be in shutting down public spaces. 

Current tests use PCR genetic tests to look for signs of the viral genome in nasal and throat swabs. That tells people with flu-like symptoms if they have an active coronavirus infection. However, the test described by the Icahn School of Medicine team can determine if a person’s body has ever been exposed to COVID-19 by looking for antibodies. 

A standard ELISA test being performed on a 96-well plate. The darker the well, the more of the target protein is present in the sample.

Your body’s adaptive immune response identifies foreign material and creates antibodies specific to them. These complex proteins then attract immune cells to deal with the invaders. Antibodies remain in the blood even after an infection has been cleared, which leaves lasting evidence of the infection. 

The test developed by the New York team is a type of immunological assay known as an enzyme-linked immunosorbent assay (ELISA). Blood serum from patients can be probed with specialized antibodies to detect the presence of COVID-19 antibodies. The paper claims this method is effective at spotting infection as little as three days after exposure. If rolled out widely, this blood test could show us how many people have been infected by COVID-19 even if they never developed symptoms. With more accurate data, we could figure out how dangerous the virus actually is.

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