Covid-19 Testing

The Covid-19 virus has many mysteries associated with it, one of those being how to test people for the virus. Testing is very important because it helps researchers track the virus and how prevalent it is. It also is necessary in order to determine an accurate death rate for the virus. The World Health Organization published a report yesterday discussing some antibody response testing being done. One type of test uses antibodies bound to a paper strip that are supposed to detect Covid-19 antigen in the respiratory tract. The WHO warns that this is not a very accurate method due to the fact the antibodies may detect human coronavirus strains and give a false positive. Another issue is that this type of test would only be positive while the virus is still actively replicating; so this test would be good for diagnosing early infection but not good at detecting the virus in someone who may have had it longer. 

The World Health Organization also discussed another type of test that detects Covid-19 antibodies in the blood. According to the W.H.O. “Studies suggest that the majority of patients develop antibody response only in the second week after onset of symptoms”.This test is not applicable unless someone has had the virus for a decent amount of time and is already in the recovery phase. While this may seem like a waste of money to some since the patient would already be past the point where intermediate intervention would help, I think it is still important. Everyone that is assumed to have Covid should be verified that way researchers can get accurate numbers when they are creating death rates or talking about the number of confirmed cases. While this is a basic explanation of antibody testing the CDC has put out a recent article that goes more into depth. 

The CDC goes into detail about how the concentration of IgG antibodies can show how long someone has been infected. According to their research “IgG seroconversion can be reliably confirmed in the second week after disease onset”. This means that B cells have begun affinity maturation and class switching. IgG is much more capable of binding to an antigen than IgM, so as time goes on IgM is clipped out of the B cell DNA and only IgG is made. If someone had only IgM this would mean they were newly infected and the adaptive immune response was just barely started. If a tested patient had both IgG and IgM then that means class switching has started, which is probably in the second week of disease for Covid-19 as stated by the CDC above. If a person were to only have IgG antibodies then that would mean the person had the infection a while ago and had fought it off and developed immunity to that specific strain. That person would no longer be contagious because having only IgG antibodies indicates they were infected a long time ago. 

In conclusion, I have to add this random thought that I had. I think that I am extremely fortunate to be learning about how viruses and testing work at the exact same time that this global pandemic is occurring. It is so interesting to be able to learn while using the current event that is all over the news as an example. It also makes me feel more educated when I speak about the virus to my family and friends. If this crisis had happened last semester then I never would have understood how testing works in the way that I do now.