COVID-19: A virus haunted world
In a world that has been dominated by a fierce virus that dared to cross the species barrier, there lived the greatest integration of politics, economics, science and medicine. People of all backgrounds collaborate and determine the best possible way to eliminate the very threat of our own existence.
Late in December 2019, pneumonia cases of unknown origin in Wuhan China began to spread rapidly . Later, scientists determined a novel coronavirus (CoV) to be the causative agent of the new emerging disease. This virus causes coronavirus disease 2019 (COVID-19) and was termed Severe Acute Respiratory Syndrome (SARS)-CoV-2, for its genetic similarities to SARS-CoV, the etiological agent that caused the first pandemic of the century . In March 2020, the World Health Organization (WHO) declared COVID-19 a pandemic. As of February 2021, COVID-19 has been responsible for approximately 125 million cases and has taken over nearly 3 million lives worldwide . In the span of one year, scientists have successfully developed the first mRNA-based vaccine for a coronavirus that confers over 95% protection against infection . However, the development of a vaccine does not suggest the end of the pandemic- as SARS-CoV-2 continues to mutate. We now worry about the effectiveness of current vaccines against these new variants. In this article, I will give a brief overview of our current understanding of COVID-19, our major concerns, and how we can improve our circumstances.
What is the origin and pathology of SARS-CoV-2?
To better understand COVID-19, the origin of SARS-CoV-2 should first be identified. SARS-CoV-2, like SARS-CoV and Middle East Respiratory Syndrome (MERS)-CoV, is a β-CoV that belongs to the family Coronaviridae within the Nidovirales order . The subfamily Orthocoronavirinae is further divided into four genera: alpha, beta, delta, and gamma. Alpha and beta CoVs are known to infect humans, other mammals, and a wide array of other animals, while delta and gamma CoV are known to infect birds . Studies have shown an origin of CoVs associated with bats as a natural reservoir due to the genetic similarities in SARS-CoV-related viruses found in horseshoe bats (genus Rhinolophus) . The transmission between bats to humans often requires an intermediate host. For example, SARS-CoV crossed the species barrier from bats to palm civets to humans, while MERS-CoV went from bats to dromedary camels to humans [7-9]. While it has yet to be confirmed, SARS-CoV-2 may have transmitted from bats to pangolins to humans .
CoVs are enveloped RNA viruses, with a genome containing 10 identified genes and 14 open-reading frames (ORFs) encoding 27 proteins. Two-thirds of the genome facilitates the formation of an environment for viral replication, the replication-transcription complex (RTC), and the remaining third of the genome encodes structural proteins that are necessary for virion formation . The club-like spike proteins surrounding the virus is the most definitive feature of all coronaviruses. Its name is derived from the Latin word corona, meaning “crown.” Like SARS-CoV, SARS-CoV-2 makes use of the host receptor angiotensin-converting enzyme 2 (ACE2) to gain entry and infect host cells . Upon virion assembly using host machinery, the virus is then released through exocytosis without rupturing the cell membrane .
What is COVID-19 and how can we detect it?
While individuals of all ages can be affected, COVID-19 disproportionately affects the elder population and those with pre-existing, chronic health conditions . Meta analysis from a study discovered that patients with hypertension, cardiovascular diseases, diabetes, smoking habits, chronic obstructive pulmonary disease (COPD), and chronic kidney disease exhibited severe COVID19 symptoms marking these as the most frequent underlying conditions reported in hospitalized patients . SARS-CoV-2 predominantly infects the lower respiratory tract and causes pneumonia in humans . COVID-19 patients will either be asymptomatic or express mild, moderate or severe symptoms. The majority COVID-19 patients suffer from mild flu-like symptoms including fever, dry cough, fatigue, expectoration, dyspnea, headache or dizziness, diarrhea, nausea, and vomiting .
There are currently two types of tests for COVID-19: diagnostic and antibody tests. Diagnostic tests are used to confirm active infection and consist of molecular tests, such as RT-PCR and antigen tests. RT-PCR detects viral genetic material and viral proteins such as the S protein. Researchers have also developed a test using RT-PCR to detect negative cases of SARS-CoV-2 using the SYBR Green methodology, a dye that binds the minor groove of double-stranded DNA, increasing the fluorescence intensity . Antibody tests are used to determine previous exposure to the virus by detecting levels of antibody specific for the virus, but do not confirm active infection, therefore, are not used for diagnosis. While diagnostic tests can confirm active infection, they cannot confirm whether the patient is infectious or not. This highlights the need for the development of an assay to determine the infectious state of the patient in order to prevent further spread.
By understanding the basic principles of COVID-19, including its origin, disease progression and detection we can now move towards understanding vaccine development.
While researchers worldwide contribute to the overall understanding of SARS-CoV-2 and COVID-19, there is still much more to learn. It is critical to understand that SARS-CoV-2 will not be the last pathogen to invade humanity. Instead we should look at the 2020 pandemic as a form of preparation to future invaders. While there are many factors that contribute to controlling a pandemic, such as medicine, politics and economics, research directed towards vaccine development will help in the prevention of infection and disease. If you would like to learn more on COVID-19, stay tuned for our next blog on COVID-19 vaccines!
Written by Ruby Escobedo, B.S., Ph.D. student
Edited by Thu Duong, B.S., Ph.D. candidate
This article is for information purposes only. Consult a licensed medial provider for advice and treatment specific to you.
This article was written in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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