The disease COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA load. But how much do we know about the disease and how can we cut through the thick layers of public disinformation?
To gain a scientific insight into COVID-19, Digital Journal spoke with Sara Winokur. Sara is a geneticist, researcher, and author and she has a master’s degree in cytogenetics and a Ph.D. in molecular genetics. Her research helped identify mutations underlying muscular dystrophy, Huntington’s disease, dwarfism, and a rare craniofacial syndrome. She continues to work as a consultant on potential therapies for genetic disease.
Digital Journal: How serious is COVID-19?
Sara Winokur: COVID-19 stands for COronaVIrusDisease-2019. Coronaviruses are a family of viruses which can cause illness. In humans, several coronaviruses are known to cause respiratory infections, some of which are mild, such as the common cold, while others are more severe such as Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS). The recent pandemic COVID-19 is related to SARS but ranges in severity, with some individuals displaying no symptoms at all, the majority have mild or moderate illness and recover from the disease, and some patients suffer from a severe respiratory illness that can prove fatal.
DJ: Why do viruses cause disease?
Winokur: Viruses are not truly living organisms. They cannot move, create energy, or replicate on their own. They are dependent on a host organism to provide these functions. Viruses are simply bits of genetic material—either DNA or RNA—surrounded by an envelope of protein and lipids. The current coronavirus SARS-CoV-2 is an RNA molecule that has a protein on its surface which latches onto a receptor called ACE2 in the lining of the lung. When the virus attaches to the receptor, it enters the cell and hijacks the cell’s machinery in order to make copies of itself. After tens of thousands of copies are made, the cell bursts and the new virus particles can attack other cells. This particular virus can cause severe respiratory disease because cells in the lung are damaged and no longer able to transport oxygen into the bloodstream. Some symptoms of disease such as fever and fatigue result from the activities of the immune system trying to eliminate the infection from the body. Heat (fever) inactivates viruses and fatigue results from the high energy demands of the immune system fighting the virus.
DJ: How did COVID-19 come about?
Winokur: The first human cases of COVID-19 were identified in Wuhan City, China in December 2019.
The source of SARS-CoV-2, the coronavirus (CoV) causing COVID-19 is not completely understood but it is believed to be a zoonotic virus, which means it is a virus that ‘jumps the species barrier’ and can be transmitted between animals and people. MERS was transmitted from bats to camels to humans and SARS from bats to civet cats to humans. Strong evidence suggests the virus causing COVID-19 originated in bats then transmitted to humans via pangolins. Although SARS-CoV-2 is very similar to the bat and pangolin virus, it has evolved so that it has a an extremely strong affinity for the human ACE2 receptor on human lung cells. Initial suspicion that the virus may have been created in the lab is unfounded since the mutations which allow the virus to attach so strongly to the human ACE2 receptor are found in nature and would not have been predicted by computer and scientific modeling.
DJ: What will be the impact of the coronavirus on our DNA?
Winokur: Some viruses like HIV and varicella (chickenpox) can lie dormant in the body and reappear at a later time to cause symptoms. HIV is a retrovirus which means that it is an RNA virus that, once inside the cell, makes DNA copies of itself which can then integrate into the human genome (DNA). The varicella zoster virus initially causes chicken pox but then can lie dormant in the nerve cells and cause shingles later in life. While neither of these scenarios appear to be the case with the SARS-CoV-2 virus that causes COVID-19, there is still much that is not known about both the virus and the disease.
DJ: Will antivirals work against the coronavirus?
Winokur: The short answer is yes, there will be antivirals that can help reduce symptoms of COVID-19 and the course of the disease. These will be especially important as treatments until a vaccine is widely available which best estimates predict 12-18 months from now. None of the current medications being discussed and delivered under a compassionate use program have cleared the rigorous clinical trials necessary to ensure not more harm than good results from their use. Perhaps the most promising antiviral currently is remdesivir. This drug works by tricking the viral RNA into incorporating a ‘faulty’ nucleoside (the building block adenosine) so that the virus can replicate properly. Another drug NHC works similarly by mimicking another nucleotide cytosine. The antimalarial drug hydrochloroquine helps stop the virus from invading the cell and also tamps down an overactive immune system. While there certainly is hope, these antivirals, as well as others in the pipeline, need to undergo more complete clinical trials.
DJ: Could some people have a natural immunity?
Winokur: There are two types of immunity: natural (innate) and acquired. Natural immunity is our immune defense that is present by birth without prior exposure to pathogens (viruses, bacteria, fungi, etc.). Natural immunity provides an immediate response to foreign invaders by recruiting white blood cells and other components to attack the pathogen. However, this response treats all foreign invaders in much the same way.
Unfortunately, we do not have a natural immunity that is specific to COVID-19. Our immune systems react in ‘damage-control’ mode, triggering white blood cells to spring into action. Many of the symptoms that make a person suffer during an infection—fever, malaise, headache—result from the activities of the immune system trying to eliminate the infection from the body. But the natural immune system cannot specifically target the COVID-19 virus. That specific attack on the COVID-19 virus can only be accomplished by acquired immunity, which develops only when our body is exposed to pathogenic antigens (e.g. viral particles or bacteria surface proteins). This exposure leads to our immune system developing antibodies after either an infection or vaccination.
That being said, some people seem more susceptible to the disease and there may well be genetic factors that make others more resilient. There definitely is an age bias. Children under 10 account for only 1% of cases while adults 30-70 years old account for 87% of cases. Seniors are much more likely to be severely affected, just as they are with seasonal flu. This may be because they have weaker immune systems, underlying health problems, or live in residential senior communities. Another possibility is that the lining of their lungs may contain more receptors for the virus to latch onto. Many individuals may actually be more resilient to the disease since they have mild or moderate—and even no—symptoms. Whether this is due to genetics, lifestyle, or exposure to lower doses of the virus, we just don’t know.
DJ: Why does a vaccine take so long to develop? When do you think we’ll see a COVID-19 vaccine?
Winokur: A vaccine works by training the immune system to recognize and combat pathogens. To do this, certain molecules from the virus or bacteria must be introduced into the body to trigger a response. The immune system can then safely learn to recognize the pathogens as hostile invaders, produce antibodies, and remember them for the future. If the bacteria or virus reappears, the immune system will recognize the antigens immediately and attack aggressively well before the pathogen can spread and cause sickness.
A vaccine will not be available for some time, as the development of the vaccine, and then safety and effectiveness outcomes will have to be determined. Those that have had the disease will have antibodies to fight off future infections, but for those of us that have not been exposed to the virus, it will be essential to be vaccinated.
Vaccines don’t just work on an individual level, they protect entire populations. Once enough people are immunized, opportunities for an outbreak of disease become so low even people who aren’t immunized benefit since the virus won’t be able to establish a foothold in the population. This is called ‘herd immunity’. We all need to consider how our actions affect others.
Now, more than ever, we need to protect those among us who are most vulnerable and cannot be immunized: infants, young children, the elderly, people with severe allergies, pregnant women, or people with compromised immune systems. Let’s come together to help one another and keep our distance as this is the most important kindness we can extend to others during this time of the COVID-19 pandemic.
