Test and trace is an accepted way of trying to limit the number of people each person with an infection passes it on to. This method is now being used to combat COVID-19. By testing people with symptoms, doctors find out whether they have SARS-CoV-2, the virus that causes COVID-19. If the person does have SARS-CoV-2, contact tracers then contact everyone that person has recently been in close contact with. These people are told to isolate themselves at home to stop them spreading the virus. If they develop symptoms they will also be tested.
There are two type of testing available for COVID-19: viral tests and antibody tests.
1. A viral test tells you if you have a current infection.
2. An antibody test might tell you if you had a past infection. An antibody test might not show if you have a current infection because it can take 1–3 weeks after infection for your body to make antibodies. Having antibodies to the virus that causes COVID-19 might provide protection from getting infected with the virus again. If it does, we do not know how much protection the antibodies might provide or how long this protection might last.
Testing in India:-
| Sample tested | tested positive | Test per 1 million people | Percentage tested positive |
|---|---|---|---|
| 11,587,153 | 849,553 | 8,397 | 7.33% |
Different methods of testing:-
1.Rapid diagnostic test (RDT):
RDTs typically use a small, portable, positive/negative lateral flow assay that can be executed at point of care. RDTs may process blood samples, saliva samples, or nasal swab fluids. RDTs produce colored lines to indicate positive or negative results.
2.Enzyme-linked immunosorbent assay (ELISA):
ELISA can be qualitative or quantitative and generally require a lab. These tests usually use whole blood, plasma, or serum samples. A plate is coated with a viral protein, such as a SARS-CoV-2 spike protein. Samples are incubated with the protein, allowing any antibodies to bind to it. The antibody-protein complex can then be detected with another wash of antibodies that produce a color/fluorescent readout.
3.Neutralization assay:
Neutralization assays assess whether sample antibodies prevent viral infection in test cells. These tests sample blood, plasma or serum. The test cultures cells that allow viral reproduction (e.g., VeroE6 cells). By varying antibody concentrations, researchers can visualize and quantify how many test antibodies block virus replication.
Tracing in India:-
In India, the tracing app Aarogya Setu (“bridge to health”) has been downloaded more than 100 million times and was the seventh most downloaded app worldwide in April. Using a phone's Bluetooth and location data, Aarogya Setu lets users know if they have been near a person with Covid-19 by scanning a database of known cases of infection. The data is then shared with the government. If you've met someone in the last two weeks who has tested positive, the app calculates your risk of infection based on how recent it was and proximity, and recommends measures.