INTRODUCTION
Coronaviruses are viruses from the family coronaviridae and subfamily ortho coronaviridae that usually cause mild and severe respiratory distress in man and other animals. Three types of viruses causes severe diseases to humans; SARS-CoV that cause severe acute respiratory syndrome, MERS-CoV that cause Middle East respiratory syndrome and the currently discovered SARS-CoV-2 (David and Steven, 1996; CDC, 2020; NIM, 2020).
Viral respiratory illness commonly known as severe acute respiratory syndrome is caused by SARS associated coronavirus (SARS-CoV) generally called SARS virus. It is a recently recognized febrile respiratory illness that first appeared in Guangdong Province, southern part of People’s Republic of China in November 2002 (Sampathkumar et al., 2003; Kang et al., 2005; Maschinen et al., 2005), has since spread to more than two dozen countries in North America, South America, Europe, and Asia. The SARS global outbreak contained (CDC, 2017) has resulted in a cumulative total of 8422 cases, with 916 deaths reported from 29 countries during the outbreak (Sampathkumar et al., 2003; WHO, 2003; Maschinen et al., 2005). A global case-fatality ratio of 11% was recorded (WHO, 2003). World Health Organization (WHO) announced that the last chain of human transmission was broken on 5 July 2003. Since 2004, there have not been any known cases of SARS reported anywhere in the world (CDC, 2017). (Cheng, et al., 2020)
The incubation period of SARS is generally between 2– 12 days (Maschinen et al., 2005) which was estimated to be 6.4 days with mean incubation time of 3-5. The disease usually presents with fever, chills, dry cough, malaise, headache, myalgia and dyspnoea; sore throat, rhinorrhoea, vomiting and diarrhoea, symptoms may mimic other respiratory diseases such as influenza, pneumonia or bronchitis (Hui et al., 2004).
Detection of SARS CoV using real time polymerase chain reaction (RT-PCR) was not reliable at early stage of the disease (Kang et al., 2005), whereas serologic confirmation takes more than 2 weeks to achieve good result. Serum quantitative assessment of SARS-CoV RNA with RT-PCR constitutes only about 80% result at early days of infection (Hui et al., 2004).
At the end of the year 2019, a novel coronavirus was identified in China presenting with respiratory distress that mimic pneumonia (Mcintosh and Martin, 2020) that later disseminated into Asia, Australia, Africa, and European regions, and subsequently spread worldwide into different countries including Japan, Italy, Germany, South Africa, Singapore, United Kingdom and the Unites States (Elflein, 2020;Wu et al., 2020). The virus was initially called 2019-nCoV-2 and later renamed as severe acute respiratory syndrome virus type 2 (SARS-CoV-2) and the disease called corona virus disease 2019 (COVID-19) in February 2019 by the WHO (McIntosh and Martin, 2020) and subsequently declared as world emergency. COVID-19 has the ability to spread rapidly having impact socioeconomically and medically around the Globe (CDC, 2019; FDA, 2020). The disease affect commonly the middle age, older individuals and immunosuppressed, however, the later have the likelihood of severe disease. It has incubation period of 2-14 days following exposure, most cases occurring 4-5 days (McIntosh and Martin, 2020) with most patients being asymptomatic at the initial stage (Fuk-Woo et al., 2020; Shi et al., 2020). Many individuals present with high fever, fatigue, dry cough and myalgia; dyspnoea and hypoxia that progress to acute respiratory distress syndrome (ARDS) results, and subsequently organs failure (Wu et al., 2020). Currently (as at May 9), COVID-19 accounts for over 4.8 million cases, more than 316, 000 deaths, over 1.85 million recoveries and 2.5 estimated infection rate in about 216 countries and territories worldwide (ECDC, 2020a; WHO, 2020). Higher cases (over 1.87 million) with 165,995 deaths were reported in the European region and the lowest incidence being reported in Oceanian region with as low as 8,440 cases, about 126 deaths and over 8,000 recoveries). About 589.9 cases per million cases and 40 death per million population have been reported Globally (CDC, 2020; ECDC, 2020; Elflein, 2020; Roser et al., 2020; WHO, 2020).
Generally, viral infection can be diagnosed in the laboratory through detection of viruses from nasal swab, pharyngeal swab, broncho-alveolar fluids, sputum and or bronchial aspirates and blood by Electron microscopy, viral antigens, nucleic acid, specific antibodies and by isolation (James, 2017; Huang et al., 2020). Detection of nucleic acid is achieved by polymeraase chain reaction (PCR), i.e nucleic acid amplification test (NAAT) whereas antigen and antibody are detected by serologic techniques such as Enzyme Immunoassay - ELISA, Serum neutrallisation assay, Western blotting, Immunodiffusion, Immunoflourescence, haemagglutination inhibition assay and Class specific antibody assay (Reller & Weinstein, 2000; James, 2017). Similar specimen and procedures apply to common respiratory viruses such as adenoviruses, parainfluenza virus, avian influenza, MERS-CoV respiratory syncytial virus, influenza virus including COVID-19 and SARS-CoV (Huang et al., 2020). SARS-CoVs were known to spread very fast, hence the need to have a method of detection that is easier, faster, reliable and economically adaptable more than the currently used techniques especially at point of care.