Since March, COVID-19 virus has also broken out in other countries except China. Many countries generally face the problem of insufficient detection capacity and detection kits. So what is the principle of detecting virus with kit? What's high-tech in this?
Detection principle
Except for prions, all other viruses are composed of nucleic acids wrapped in the shell of protein. There are three main methods to detect this kind of virus:
Nucleic acid detection: A special fragment of virus genetic material (professional name target gene) is detected, which proves the existence of virus.
Antigen detection: Detecting the surface protein or internal nuclear protein of the pathogen can also prove the existence of the virus.
Antibody detection: The immune system will produce specific antibodies against the invading antigens, and the detection of the corresponding antibodies can also prove that the virus has been infected.
Among them, it takes several days for antibodies to be produced in the human body, and people with low immunity may have a small number of antibodies, resulting in false negatives. Antibody testing is generally suitable for rehabilitation testing.
COVID-19 belongs to single-stranded RNA virus, and nucleic acid detection is very suitable. The general steps of detection are as follows:
Step 1: Wipe the patient's throat with a cotton swab to get the pathogen.
Step 2: put the virus into the nutrient solution, so that the number of viruses expands hundreds of times.
Step 3: Pour into another bottle, and the inhibitor inside can kill other creatures except the virus.
Step 4: Isolate the virus and add special detection solution to let the virus develop.
According to different detection principles, the detection method and time may be different. For example, the common fluorescence quantitative PCR, after isolating the virus RNA, reverse transcribes the RNA into DNA, and then makes the product fluoresce through a series of complex reactions. Each DNA strand can produce a fluorescent molecule, which can be detected by instruments.
Production of kit
As long as you have the nucleic acid sequence of the virus, it is not difficult to produce a virus detection kit. Many pharmaceutical companies can produce it. Various common virus detection reagents are sold online, and hospitals also have some commonly used virus detection and chemical component detection kits.
However, for a brand-new virus, from R&D to mass production, it is not only the R&D ability of enterprises that is tested. For example, when COVID-19 broke out, a pharmaceutical company said anonymously in May 438+10 that the whole company had implemented three shifts, but 65438+ 10,000 people per day was the limit of production.
Considering the existence of false negatives, it is necessary to test a single person repeatedly, so the demand for COVID-19 kits is great; When producing the kit, testers need to touch the body fluids or blood of suspected patients, which is very dangerous for COVID-19, at least in P3-level laboratories.
Generally speaking, the whole nucleic acid detection process takes 2~6 hours. If the time of sample collection, sample transfer and waiting is included, it will take 1~2 days from collection to result. Some new detection methods may shorten the detection time, but whether it can be mass-produced and how accurate it is is also a problem.
China is the only country in the world with a complete industrial chain. Some enterprises can change the product types in a short time, such as BYD producing drawings in three days, producing automatic mask machines in seven days, and exporting masks in 10 days, which are the embodiment of the country's complete industrial chain.
The same is true for virus detection kits. It is difficult to realize large-scale production in a short time. The production of biological enzymes, the sub-packaging of kits and the supply of raw materials are all problems. I believe that few countries in the world can do it, but our country has taken the lead. For other countries with incomplete industrial chains, raw materials may be a problem.