As of late, the world is facing a new pandemic disease that is quickly spreading around the world. The causative agent or virus responsible for this pandemic, COVID-19, or novel coronavirus is SARS-CoV-2 [Severe acute respiratory syndrome coronavirus 2].
Virus Source & Prevalence
COVID-19 is a large family of many viruses. They are common in different species including Homo-sapiens, Miniopterus paululus, Felis catus, Bos taurus, and Camelus dromedarius. Furthermore, animal COVID-19, in rare cases can also infect Homo-sapiens just like SARS-CoV & MERS-CoV.
According to the World Health Organization, SARS-Cov-2, SARS-Cov, and MERS-CoV originate in bats. The sequences taken from US & China patients are similar to each other, suggesting the origin is from an animal reservoir. At the beginning of this pandemic, in Wuhan, China, people were in direct contact with animal & seafood markets. Resulting in the spreading of this disease quickly. Interestingly, some patients had no exposure to animal & seafood markets. This indicates that the mode of transmission is one person to another. Reports for a person to person prevalence outside of China in other countries and the US isn’t an exception. Furthermore, there are reports for COVID-19 outbreaks in many other countries like Italy, Germany, and France.
Symptoms of SARS-COV-2
The Symptoms of COVID-19 are numerous; the most common are fever, tiredness, chest pain, cough, and breath shortness, headache, in addition to the loss of taste & smell and fever. Furthermore, the above symptoms are not present in all cases. As some of them might experience a few of them or may not have any of them all. Also, patients with chronic signs may experience organ failure. The incubation time ranges from 2-14 days.
Severity of COVID-19
The COVID-19 complete clinical picture is not complete yet. According to reports, the severity of COVID-19 ranges from mild to severe. The variation between cases is quite significant; as in mild cases, patients may not experience symptoms and considered asymptomatic; however, in severe ones, it might lead to death. Additionally, according to a report the severity of the disease appears in 16% of the total of infected persons; also those with serious medical conditions are at a higher risk of developing the illness; medical conditions like diabetes, heart disease, and autoimmune diseases might be the main reason for developing COVID-19.
Risk Factors of Disease Severity
Centers for Disease Control and Prevention clarified that there are many disease severity risk factors; however, such factors need many studies to be perfectly-understood clearly; as COVID-19 is a new disease and still need many research studies. Additionally, it differs with age; as in children, severe conditions include problems in hemoglobin level, respiratory tract, pulmonary hypoplasia, and heart diseases.
Also, those whose status is immunocompromised – as a result of long-term immunosuppressant use – indicate a higher risk for disease severity. One of the disease risk factors is dyspnea, the breath shortness/air hunger. Other risk factors might be pregnancy and the use of certain medications.
In China, the old people were at a higher risk to develop the severity of the disease especially those having disease and disease-associated complications like cancer, diabetes, hypertension, and cardiovascular diseases.
Assessment of Risk Factors
A research group after carrying out a study that synthesizes the available evidence and provides judgment on the consistency of the association between risk factors and a composite end-point of severe-fatal COVID-19, they have conducted risk factors analysis across seventeen different studies. According to them, total of 60 predictors for disease-severity, of which seven were of high consistency, 40 of medium, and 13 of low. Furthermore, the highest risk factors with the great association are d- dimer, body temperature, diabetes, age, SOFA [score sequential organ failure assessment score], and albumin.
Out of all those risk factors, diabetes is being the most consistent comorbidity predicting disease severity; therefore, we should focus on the comparability of reporting cases; in addition to the factors & outcomes alongside with natural history of COVID-19 different stages. Interestingly, diabetes has been also reported to other respiratory virus disease severity called ARDS [Acute respiratory distress syndrome]. We can explain this through the immunosuppressive effect of hyperglycemia and that why diabetic patients could develop ARDS. There are also many limitations to such a study; the most important one appears in China which surely limits the external validity of other countries’ risk factors.
It is so vital to be aware of risk factors because COVID-19 patients actually will need hospitalization or intensive care; additionally, risk factors help patients to better understand SARS-COV-2 and to anticipate treatment they might need afterward. Moreover, it also helps them to reduce the COVID-19 severity risk by trying to manage any conditions they might experience.
Diagnosis of SARS-COV-2
There are a plethora of disparate diagnostic techniques to be carried out for the detection of SARS-COV-2, however, each one of them has certain advantages & few disadvantages as shown in the table below.
However, the diagnosis of such a disease isn’t an easy task because there is Antigenic cross-reactivity between SARS-CoV-2 and other viruses like dengue. According to research, cross-reactivity is possible between dengue viruses & SARS-CoV-2 since they do have shared features and similar presentations. Therefore, the possibility of cross-reactivity occurrence is 21.8%. As a result, this is going to lead to false-positive dengue serology among COVID-19 patients and vice versa. Consequently, this will make many serious consequences to both patients & public health.
|Neutralization tests||VNT and PVNT||BSL-2 or BSL-3, Pathogen Laboratories||simple, low-cost, high specificity high sensitivity||Time-consuming, laborious, Complex pre-treatment steps|
|PCR||qRT-PCR||BSL-2, public health institutes||time-saving|
|BSL-2||High sensitivity||complex, false negative, Complex pre-treatment|
|Nested RT-PCR||health institutes,|
|copy-number||amplification may cause cross-contamination|
|ddPCR||BSL-2, public health institutes, Quarantine centers||Quantitative, sensitive||Susceptible to exogenous contamination, expensive than qRT-PCR|
|Nanoparticles – based amplification||BSL-2||High sensitivity, automated RNA extraction, excellent RNA binding performances||Complex, expensive than qRT-PCR, with the risk of photobleaching|
|RT-LAMP||Basic laboratories, community nursing sites||fast and rapid||high-risk contamination, false-positive, nonspecific amplification|
|Portable benchtop- size analyzers||Clinical laboratories||Automatic, portable||inconsistent, insensitivity|
|ELISA||Clinical laboratories, public health institutes||Quantitative detection, simple||Time-consuming, low sensitivity, cross-reactivity, expensive|
|IFA||Clinical laboratories, public health institutes||Avoid the interference of endogenous biotin and contamination of antigens in the blood|
|Non-specific fluorescence, subjective, low- throughput, time- consuming|
|CLIA||Clinical laboratories||Automatic, rapid||sophisticated instruments, high requirements for equipment and environment, not suitable for detect whole blood samples|
|LFA||Clinical laboratories||Rapid, convenient, on-site screening, inexpensive||Low sensitivity, cross-reactivity, inconsistent|
|Microarray and microfluidic chip||Clinical laboratories||Small size, high sensitivity, automatic||Core technologies lack norms and standards, high cost, nonspecific|
|Genome Sequencing||Meta-transcriptomic sequencing||BSL-2, genetic testing centers, research laboratories||Simple, reduce the cost, does not claim a reference sequence||Increase cost, insufficient coverage, and Depth|
|Nanopore sequencing||BSL-2, genetic testing centers, research laboratories||Broad detection range, rapid, high-accuracy||expensive|
|Hybrid capture-based sequencing||BSL-2, genetic testing centers, research laboratories||High sensitivity, suitable to detect intraindividual variations||expensive instruments, not suitable to sequence highly diverse or recombinant viruses|
Treatment of COVID-19
Currently, studies are being made continuously in view to tackling the COVID-19, and one of the most important studies has been carried out in Italy which showed clear findings that eculizumab could be used for such a purpose, the study has been carried out on four COVID-19 patients having clear signs & symptoms of SARS-COV2 with eculizumab; and surprisingly, their C-reactive protein test results have been returned to approximately the normal ranges [dropped to 3.5 mg/dl after it was 14.6 mg/dl] within 13 days of treatment and the patients have been recovered successfully which suggests a very good perspective for the use of such a drug in the COVID-19 treatment protocol.
Remdesivir can also be used in the treatment protocol and this has been concluded after making a study on sixty-one COVID-19 patients who were having low levels of oxygen, by applying a course of Remdesivir, 36 of the total number had a clear improvement and increase in the levels of oxygen.
Till now there is no approval for any medications for treatment purposes. In conclusion, COVID-19 is a serious condition that needs special precautions not only from patients but also from their families. Currently, we need to research further, to find out more about COVID-19.