[Date of latest publication cited: November 12, 2020]
Like many viruses, coronaviruses can take several forms: whole, viable viruses, called virions, or incomplete virus particles. The virions can enter cells and get them to replicate more viruses while destroying the cells, but the virus particles cannot. Scientists did most of the following research studies using different methods of polymerase chain reaction (PCR) tests to search for the virus’s genome, made of ribonucleic acid (RNA):
- real-time polymerase chain reactions (RT-PCR)
- reverse transcriptase polymerase chain reaction (also called RT-PCR)
- quantitative PCR (called qPCR).
The advantage of using this high tech equipment is that it can rapidly find and identify tiny amounts of viral RNA. But it identifies the RNA inside infectious whole virions, antibody-neutralized non-infective viruses, or non-infective particles with genetic material. These tests cannot distinguish between the infectious and non-infectious virus parts (Fontana et al.; Joynt; Katz; Liotti et al.; Sethuraman et al.). The PCR cycle threshold value (Ct) indirectly indicates the viral load: high Ct value shows low viral RNA quantity, and vice versa (National Centre for Infectious Diseases). So the most of the following studies indicate that SARS-CoV-2 viruses are probably transmitted by saliva, mucous, blood, feces, urine, air, and surfaces, but do not prove it.
Some scientists started using more definitive tests of culturing whole virions in cells, which is more difficult and time-consuming (Arons et al; Kujawski et al.; van Doremalen et al.; Wölfel et al.). Later, scientists will probably do more thorough studies to find if transmissible whole virions are in each body fluid or location (Brosseau; Fontana et al.).
Others tested for antibodies to SARS-CoV-2 using Enzyme-Linked Immuniosorbent Assaies (ELISA). The advantage of these is finding infection histories both during and after active infection. Their disadvantages are inabilities to detect during presymptomatic and early symptomatic periods, and variability after symptoms (Sethuraman et al.) Some discussed using positive antibody test results as certification for allowing previously-infected people to resume more normal activities, called “immunity passports.” The advantages of this are allowing those individuals more freedom to work and improve the economy (Brown et al.). Disadvantages are: inaccuracies and variability of tests; and creation of incentives to develop over-sensitive tests with false positives. Some people might to get infected, which might cause them to get seriously ill or spread infection to others (Cockburn; Hall et al.; Persad et al.; World Health Organization “Immunity…”).
No transmission mode of SARS-CoV-2 has been completely proven: for each infected case that probably was infected via one mode, that person might have been infected by another mode (Klompas et al.; WHO “Transmission of SARS-CoV-2”).