The infectious agent causing the current pandemic is a virus, not a bacterium. The official name of this virus is severe acuterespiratory syndrome Coronavirus-2 orSARS-CoV-2. The official name for the viral disease is Covid-19, which was discovered in Wuhan, China.
This virus is not the same as the coronavirus (SARS-CoV) identified in 2003, the cause of SARS, which was first noted in Guangdong, China. SARS became an epidemic that affected 26 countries.
There are two types of test available for the Covid-19.
One is the NAATS or nucleic acid amplification tests like the reverse transcription polymerase chain reaction or RT-PCR. It is the main or primary test to diagnose the disease.
Specimens are nasopharyngeal swabs or NPS (from the nose and throat), oropharyngeal swabs or OPS from the mouth and throat, and samples from the lower respiratory tract like tracheal aspirates and expectorated sputum.
Several assays are available for RT-PCR and the sensitivity or specificity of these tests differ.
Another is serologic test that measures anti-bodies to SARS-CoV-2. These are used mainly to identify patients who have had the Covid-19 in the past. Some tests may help identify patients with acute infection but the results are not as reliable and may have to be validated with RT-PCR.
False-negative tests mean that a laboratory result yields a negative result even if a patient has the viral infection.
Some patients may already have the viral disease – with signs and symptoms – plus history of travel and exposure but the RT-PCR is negative or anti-body test is negative, a ‘presumptive diagnosis” is made and the patient is still managed as the Covid-19. Medical diagnosis is still based on the patient’s history and physical examination
Initial results of the recovery trial done at the University of Oxford in the United Kingdom have shown that among severely ill Covid-19 patients on ventilators, dexamethasone a corticosteroid decreased the rate of dying by one third. Among patients requiring only oxygen, the death rate was reduced by one fifth. This beneficial effect was not noted in patients with milder disease and did not require respiratory intervention. The study was done only on hospitalized patients and did not include patients outside hospital setting.
It has been shown in a U.S. study that mutation in the SARS-CoV-2 may increase its ability to infect cells. Mutation D614G increased the number of spikes in the virus four to five times, increasing its ability to bind to human cells. Further studies are needed to establish the effect of this mutation to severity of symptoms and overall mortality rates.