#Coronavirustesting

As the world faces the Coronavirus pandemic testing has become a hot issue that people are facing in their daily lives. But the question remains, which test is best? It is likely that we will never know the answer to that question, but an understanding of the options available can certainly help the general public to make an informed decision before selecting a method of testing. According to the article from the Financial Times, titled “What coronavirus test does the world need to track the pandemic?” there are two main types of tests for the virus officially named Sars-CoV-2: Antigen tests and Antibody tests. Antigen tests are used to detect whether or not an individual is infected with the coronavirus that causes Covid-19 while antibody tests are used to determine if an individual has been infected in the past.

Antigen tests come in two varieties, a rapid version that delivers results in minutes and another using Polymerase Chain Reaction (PCR) to multiply the genetic material found in a virus containing sample from an infected individual which takes longer. Both the rapid and the PCR tests can be performed on a sample collected using a nasopharyngeal swab but can also be done using a throat swab or saliva sample.

Antigen Testing via Nasopharyngeal Swab

The virus can be detected as early a the first day of symptoms but is most accurate in the first week. This is measured by the cycle threshold where the lower values indicate positive results. No tests are always accurate but the rapid tests have been found to have more false positive and negative results than the PCR tests. In a study performed by Vermont’s Department of Health only four individuals of 65 who had tested positive with the rapid test, also tested positive with the PCR test. Because of this many states require both tests to confirm a positive diagnosis. Unfortunately, the PCR tests have also shown high incidences of false negatives. Regardless of which test is used, the accuracy still seems to be connected to the manufacturer of the test itself. Since the PCR test is thought to be the most accurate because it detects the presence of the genetic material of the virus, it is less likely to provide a false positive. As result, these are best used to identify infection as opposed to letting an individual know that they are not infected.

Antibody tests require a blood sample in order to detect the presence of antibodies against Sars-CoV-2 because once an individual is infected with the virus their immune response creates IgM antibodies that are present close to the time of infection and IgG antibodies that are produced longer after infection. These antibodies are proteins produced by the white blood cells that help to fight the virus, so if they are present in an antibody test, is clear that the individual has already been infected. When an individual is infected with a virus, lymphocytes called B cells are triggered by the presence of the antigen of that virus, and bind to the antigen using an antigen receptor. This then causes the production of cells that produce proteins called antibodies which have the same shape and structure as the antigen receptors of the B cells making them helpful in directly defending against antigens present in body fluids. Antibody tests provide a quick result and are preferred because they help people to determine if a person can return safely to society with less risk of infection.

As the pandemic became a global issue many tests began to be developed but the antigen tests were more commonly performed in the public while the antibody tests were reserved for private companies due to the need for more materials like swabs and reagents to perform the tests. Both tests are being created all over the world but some countries are producing more than others and the US was slow to get started but has increased production more recently. Because the tests must be of good quality, and the staff that are using them must be trained well, it is hard to produce them fast enough.

The spread of the SARS-CoV-2 virus, the virus that causes Covid-19, which is more notoriously known as the coronavirus, has been deemed by some to be one of the worst pandemics ever seen. With over 13.5 million cases and over 200 thousand deaths, the pandemic has taken the world by storm. In an article, Jop de Vrieze speaks on a topic that is of concern in regards to the subsiding of this virus, the topic of reinfection.

In our body, antibodies are our natural defenders. These antibodies are part of the body’s adaptive response to pathogens. Generally, B Lymphocytes(B cells) binds to an antigen and recognize it. T-Helper cells then cause the selected B cells to divide into B-Plasma cells and B-Memory cells. The B-Plasma cells then secrete antibodies which bind to the pathogen and then neutralize it, allowing Macrophages to engulf and destroy the antibody-covered pathogen. B-Memory cells help the cell be able to remember the pathogen, ultimately preventing reinfections. Antibodies are defined by Mayo Clinic as “proteins produced by your immune system in response to an infection. Your immune system — which involves a complex network of cells, organs and tissues — identifies foreign substances in your body and helps fight infections and diseases.” When you contract the virus, your body develops these antibodies that can help provide protection. But there’s a catch. The CDC says that ” we do not know how much protection the antibodies may provide or how long this protection may last,” which opens up the possibility for reinfection.

Man Getting a Covid-19 Test

Specific to de Vrieze’s article, a man in Hong Kong tested positive for the coronavirus in March and tested positive again in August, becoming the first official reinfection case. Neurologists have, reasonably, expected much milder symptoms from reinfection cases, but that hasn’t been the case for some. As the CDC stated, the amount of protection and the protection’s longevity is still a big question. The leading case in de Vrieze’s article was that of Sanne de Jong. After having the virus and mild symptoms in Mid-April, she tested negative in May and then tested positive again in June. What is so special about her “reinfection” case is that when her virus samples were taken, they were very similar. This is of significance because it correlates to another, yet more unlikely, theory mentioned in the article. When the article was written, “no proof exists of mutations that would make the virus more pathogenic or that might help the virus evade immunity. But a recent preprint by a team at the Swedish Medical Center in Seattle suggests one may exist. The team describes a person who was infected in March and reinfected four months later. The second virus had a mutation common in Europe that causes a slight change in the virus’ spike protein, which helps it break into human cells. Although symptoms were milder the second time, neutralization experiments showed antibodies elicited by the first virus did not work well against the second, the authors note, ‘which could have important implications for the success of vaccine programs.'”
The possibility of reinfection is rare but is still very possible. And other mysteries of the coronavirus are still present. Here is my advice: Play it safe. With the uncertainty and danger surrounding the virus, the best thing we can do is prevent the spread and protect ourselves and others. The need for concern can pass if we are simply patient.

BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: #Coronavirustesting

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