The most important part of stopping a disease, is to know who spreads it. To know that, you should know who is infected and isolate them from spreading it further. That is why there have been several tests invented to check if a person is a carrier of the new COVID-19.
COVID-19 is a new virus that belongs to the betaCoVs category. It’s around or elliptic and frequently pleomorphic shape, and a diameter of roughly 60–140 nm. As with other CoVs, it’s sensitive to ultraviolet rays and warmth. Additional these viruses could be efficiently inactivated by lipid solvents including ether (75 percent), ethanol, chlorine-containing disinfectant, peroxyacetic acid and chloroform except for chlorhexidine. The virus is known to infect both humans and animals, even though this new strain has not been seen in humans before 2019 in Wuhan, China.
There are two main pathways for spreading: from individual to person through respiratory droplets when an infected individual coughs or sneezes, and out of contact with infected surfaces, in which the virus may survive for hours at a time. In cases like this, someone could get COVID-19 by touching a face which has the virus onto it, then touching their eyes, mouth or nose. The virus uses the protein ACE2, which is on the surface of the cells in our lung, throat and intestinal tract to enter the cell and start producing viral proteins.
Most common symptoms of COVID-19 are:
- Shortness of breath
Incubation period is known to be 5,1 days, while first symptoms may appear anywhere from 1 to 14 days after an individual is exposed to COVID-19.
Detection of the COVID-19
Up to now there are both PCR and rapid tests available. Below you will find what the difference between them is, and which one is the better choice.
The RT-PCR, also known as real-time reverse transcription polymerase chain reaction, detects nucleic acid from SARS-CoV-2 in upper and lower respiratory specimens. The samples used are: nasopharyngeal extracts, deep cough sputum, alveoli irrigation fluid for a qualitative detection of the viral DNA, which is transcriptased to DNA with reverse. The SARS-CoV-2 RNA is generally detectable in respiratory specimens during the acute phase of infection. The detection limit of the available tests are: 1×103 copies/ml; If the DNA that is in the sample is higher than this, the result is considered to be positive. A false negative test may occur if the test is done too early, and the viral DNA hasn’t been replicated to the detection limit of the test. That is why, the test should not be done before the start of the latent period, which for COVID-19 is 5,1 days (as average). Positive results do not rule out bacterial infection or co-infection with other viruses.
qPCR kits are:
- More expensive
- Need a RT-PCR cycler
- Need more time for results (at least a day)
- Detect the virus quicker, and more rapidly.
- More accurate
- Need a sample from the nose or the throat
A rapid test incorporates both immunoassay techniques and chromatography principles by fixing highly specific antibodies and antigens onto a nitrocellulose membrane. These tests detect IgM and IgG, or IgM only. In the first version, the test has 3 fields: anti-human IgG is coated in IgG test line region, anti-human IgM is coated in IgM test line region, and a control zone, which indicates that the reagents are working. IgM antibodies are the first antibodies to be produced as a response of the infection, and they are presents as long as there are antigens in the organism. The second version of the tests, they detect only IgM antibodies: anti-human IgM is coated in IgM test line region, and a control zone, indicating that the proper volume of specimen has been added and membrane wicking has occurred. The presence of IgG indicates that the infection has been in the organism for a longer time.
These tests are working with serum, plasma or blood, and the results are available in 10-15 minutes. If the test is positive, a PCR test should be done in order to confirm the diagnosis.
Interpretation of the results:
- IgG POSITIVE: There are 2 lines: The control line, and the IgG line region, indicating the infection has occurred for certain time
- IgM POSITIVE: There are 2 lines: The control line, and the IgM line region, indicating the infection has occurred
- IgG and IgM POSITIVE: There are 2 lines: The control line, and the IgM line region, and IgG line region indicating the infection is ongoing.
- NEGATIVE: Only the control line is visible.
- INVALID: The control line does not appear, which may be due to insufficient specimen volume or incorrect procedure; the test should be repeated.
Rapid tests are:
- Results in 10 minutes
- No special instruments needed
- The sample is only a drop of blood
- There should be symptoms before performing the test