In this blog post, we will look at how PCR technology has been used to quickly and accurately diagnose viral infections such as Ebola and COVID-19.
In 2014, the Ebola virus struck fear into the hearts of people around the world. The Ebola virus is highly lethal, with a fatality rate of 50–90% within a week of infection. However, more important than the fatality rate is the extent of the virus’s spread. In the 14th century, the Black Death spread rapidly across Europe, killing one-third of the European population. The Ebola virus originated in West Africa but spread to countries around the world, earning it the nickname “the plague of the 21st century.” In response, countries implemented various screening measures targeting people arriving from abroad to prevent the virus from entering their borders. For example, the U.S. Food and Drug Administration (FDA) approved the emergency use of the “Light Mix Ebola Zaire rPT-PCR Test,” a diagnostic kit capable of detecting the Zaire strain of the Ebola virus, on December 29, 2014, enabling rapid initial diagnosis. How is PCR technology applied in the “Light Mix Ebola Zaire rPT-PCR Test,” and how does it enable the detection of viral infection?
Viruses invade host cells, replicate their own nucleic acids, and bind them to the host cell’s nucleic acids. Nucleic acids refer to DNA and RNA, which contain genetic information of living organisms. In Ebola virus-infected individuals, viral nucleic acids bind to specific parts of the host’s nucleic acids. By comparing these parts with those of non-infected individuals, infection can be detected. However, the issue is that a large amount of nucleic acid is required for this process, which can be easily resolved using PCR technology. PCR stands for Polymerase Chain Reaction, which means polymerase chain reaction. DNA has a structure where two strands are connected to each other, and to replicate DNA, the two strands must be separated, and then nucleotides, the basic units of DNA, must be attached one by one to each single strand. Nucleotides are composed of phosphate, sugar, and a base. There are four types of bases: A, G, C, and T. The sequence of these four bases determines genetic information. The phosphate and sugar form a protective framework around the bases. Additionally, the bases on one strand form hydrogen bonds with the bases on the other strand.
PCR technology can be divided into two stages. The first stage is DNA denaturation, where the DNA is heated to 90 degrees Celsius to break the hydrogen bonds between the bases and separate the DNA into two single strands. Here, the two separated strands are assumed to be A and B. The second stage is DNA synthesis. Nucleotides are connected to the separated single strand A, and as this process repeats, a new single strand identical to strand B is created. Therefore, the amount of DNA doubles compared to the original. At this point, the bonds between nucleotides on the same strand are covalent bonds between atoms, which are much stronger than hydrogen bonds, so a catalyst is needed to facilitate this bonding. The enzyme that acts as this buffer is Taq DNA polymerase.
PCR is significant because it can rapidly replicate specific parts of DNA. It is used to extract DNA from hair left at a crime scene and replicate it in large quantities, as well as to amplify DNA to determine whether a virus is present.
In early 2020, the coronavirus disease 2019 (COVID-19) pandemic spread worldwide. The COVID-19 virus was diagnosed using PCR technology. Due to its high transmissibility and diverse clinical symptoms, early diagnosis and isolation were critical. Countries worldwide endeavored to identify infected individuals and prevent further spread through rapid PCR testing. PCR testing amplifies the RNA of the COVID-19 virus to determine infection, enabling rapid and accurate diagnosis. As a result, PCR technology has become an essential tool for diagnosing and preventing the spread of infectious diseases.
As such, PCR technology is an important method for quickly determining viral infection and has made significant contributions to the management and prevention of various infectious diseases.
