As economists have modeled the global economic damage from the COVID-19 pandemic, epidemiologists have also modeled the estimated number of SARS-CoV-2 infections and deaths from the COVID-19 pandemic. Harvard epidemiologist, Dr. Marc Lipsitch DPhil, stated that:
There’s a chance that between 40% and 70% of the world’s adult population could end up infected with coronavirus.
Soon after the San Francisco Bay Area implemented shelter-in-place, California governor, Gavin Newsom, wrote a letter to US President Donald Trump stating that ~56% of California’s population will be infected with SARS-CoV-2 over an 8 week period.
Based on these estimates of SARS-CoV-2 infections, it is estimated that ~3.1–5.5 billion people globally with ~22.3 million Californians would contract COVID-19 if no interventions are undertaken to slow and/or eliminate the spread. If such infection estimates are true and secondary preventive methods are not fool proof, it is reasonable to expect some probability of getting infected with SARS-CoV-2 when we leave our home for places of social commonality, such as grocery shopping, which is an essential need under shelter-in-place orders. Then the question is how deadly is COVID-19?
Interestingly, how deadly COVID-19 is depends on which data set one refers to. First reported by the World Health Director-General Dr. Tedros Adhanom Ghebreyesus PhD, the global case fatality rate for COVID-19 was 3.4% in early-March 2020, however, this figure was not supported with adequate context — that is, the case fatality rate is dependent on diagnostic testing for the presence of SARS-CoV-2. This means as more individuals are tested for SARS-CoV-2, the more likely the case fatality rate will change given there is evidence that COVID-19 severity ranges from asymptomatic, mild, moderate, to severe illness. The case fatality rate provided by the WHO Director most likely was underreported given the infancy of global testing for SARS-CoV-2 and we continue to see a decrease in the case fatality rate as more individuals are tested.
During a House hearing, the director of the National Institute of Allergy and Infectious Diseases, Dr. Anthony Fauci MD, had stated that the COVID-19 mortality rate is “ten times more lethal than the seasonal flu”, which brings the estimated mortality rate for those who are infected with SARS-CoV-2 down to 1.0% (the case fatality rate for seasonal influenza is 0.1%). This is similar to the case fatality rate of COVID-19 from the isolated environment of the Diamond Princess cruise ship yet as Stanford epidemiologist, Dr. John Ioannidis MD DSc, states:
The case fatality rate there [Princess Diamond] was 1.0%, but this was largely elderly population, in which the death rate from Covid-19 is much higher…Projecting the Diamond Princess mortality rate onto the age structure of the U.S. population, the death rate among people infected with Covid-19 would be 0.125%…Adding…extra sources of uncertainty, reasonable estimates for the case fatality ratio in the general U.S. population vary from 0.05% to 1%.
Whether the true case fatality rate from COVID-19 is 3.4%, 1%, 0.05%, or some other number; it seems that ~95% of individuals infected with COVID-19 survive and continue to live on yet following headline news makes it seem like the COVID-19 pandemic is the end of the world for humanity. As Dr. Warwick McKibbin PhD has stated:
A large number of people would feel at risk at the onset of a pandemic, even if their actual risk of dying from the disease is low…it is not unreasonable to assume that individual perception of the risks associated with the new influenza pandemic virus similar to Spanish influenza in its virulence and the severity of clinical symptoms can be very high, especially during the early stage of the pandemic when no vaccine is available and antivirals are in short supply.
While public health experts may argue on the finer details of their predictions and whether the existing tools to flatten the curve are sufficient or unnecessarily burdensome, what determines whether we become an asymptomatic or severe case of COVID-19?
What can we as individuals do to not get severe COVID-19 if the likelihood of being infected with SARS-CoV-2 is relatively high?
Age as a risk factor for severe COVID-19. Based on data from the US Centers for Disease Control and Prevention’s (CDC) 18 March 2020 Morbidity and Mortality Weekly Report, the case fatality rate from COVID-19 in the US is highest in the elderly population and the risk of dying from COVID-19 decreases with age. This is consistent with case fatality rates from other countries as compiled by Dr. Diane Havlir MD during the UCSF Medical Grand Rounds on 19 March 2020. The differences in regional case fatality rates most likely are attributed to the region’s demographics — Italy’s high case fatality rates can be partly due to the greater proportion of elderly people infected with SARS-CoV-2; the region’s ability to implement a pandemic response quickly — South Korea was able to test, quarantine, and treat infected persons early on; and health risk factors of a region’s population.
Chronic disease increases the risk for severe COVID-19. As described by Dr. Michael Matthay MD from UCSF Departments of Medicine and Anesthesia, a patient with a severe case of COVID-19 typically dies from acute respiratory distress syndrome (ARDS) — a syndrome that basically results in a patient having their lungs filled with their own bodily fluids and being unable to breath adequately. How this happens is that SARS-CoV-2 infects the cells of the lungs to make more SARS-CoV-2 and then the infected lung cells ‘explode’ releasing more SARS-CoV-2 and the cycle continues (this is known as viral shedding). This viral shedding triggers the human body’s immune system to neutralize SARS-CoV-2.
While ~80% of COVID-19 cases are mild in severity, in part to the human body being able to create antibodies to SARS-CoV-2 within 6–12 days, the patients who succumb to severe cases of COVID-19 have an inflammatory and immune response that begins to cause harm to the lungs and heart and contributes to patient mortality as described by Dr. Annie Luetkemeyer MD. Therefore, patients with chronic diseases, such as but not limited to, heart disease, heart failure, high blood pressure, chronic obstructive lung disease, emphysema, asthma, and lung cancer, are at an increased risk of getting severe COVID-19. While diabetes is typically thought of as just a metabolic disease, patients with diabetes tend to have both heart and lung function issues, and hence, diabetes is considered another risk factor for severe COVID-19.
Current treatment guidelines for patients with severe COVID-19 are to administer breathing support, and if warranted, investigational treatments through clinical trials. Not all severe cases (~20% of COVID-19 cases) result in mortality, which can be attributed to assisting the patient in breathing sufficiently, through mechanical and negative pressure ventilators, to provide more time for the patient’s body to recover from the inflammatory and immune response to SARS-CoV-2. A patient with existing chronic disease seems to be at an increased risk of worst outcomes from severe COVID-19, possibly due to their body being in an already elevated state of chronic inflammation and their body being unable to cope with the additional inflammatory and immune response to SARS-CoV-2.
Understanding that the major risk factors for severe COVID-19 is 1. being older and 2. having chronic disease, helps us explain why not all elderly patients die from COVID-19 and why some younger patients do die from COVID-19. Most importantly, this helps us in understanding how we can decrease our risk of contracting a severe case of COVID-19 should we be infected with SARS-CoV-2.
Chronological age is different from biological age. While COVID-19 can be severe and fatal in the elderly population, the case fatality rates from the CDC indicate that more than just an individual’s chronological age determines their risk for severe COVID-19. The case fatality rate for patients with COVID-19 ranges from 2.7% (65–74 years old) up to 27.3% (85 years and older). Furthermore, being young does not make one invincible from being hospitalized due to COVID-19.
Rather than thinking about the standard definition of age as simply the passage of time, it is important to include as dimensions of aging the biological process of surviving (reaching longevity) and the ability to function (aging healthy). There is an often unspoken norm in modern society that as we age, our physical function must plummet — some of us begin to gain excess weight, our joints begin to creak, taking the stairs becomes more exhaustive, and chronic diseases impact our daily life, yet there are others who don’t seem to age like the rest of us — they compete in bodybuilding competitions in their 80s, perform open heart surgery on patients in their 90s, and compete in track and field events in their 100s.
By considering that 29.7% to 68.7% of the oldest age group of patients with COVID-19 in the US did not get hospitalized seems to indicate that chronological age is not the only reason why the elderly tend to have more life-threatening cases of COVID-19 than the younger population.
Chronic disease is not only for the old. Chronic diseases as the name implies used to take years to decades to manifest into clinically meaningful signs and symptoms, however, the global obesity epidemic, due in part to an overfed and undernourished populace and lack of physical activity, has contributed to the rise in subclinical and clinical grade chronic diseases in younger age groups. For example, atherosclerosis — the narrowing of blood vessels — can start forming during childhood and begins the development of heart disease, which is not only a risk factor for severe COVID-19 but is the leading cause of death in the world. Type 2 diabetes used to be labeled as ‘adult onset diabetes’ as it previously was thought to only occur in older adults, however, type 2 diabetes now affects both adults and children. Similar increased prevalence of high blood pressure, asthma, and cancers can be seen across all age groups.
While there is an increased prevalence of chronic disease burden across all age groups, it can be reasonably hypothesized that both the duration and severity of chronic disease burden increases the risk that an individual with chronic disease contracts severe COVID-19 regardless of chronological age. The longer a person has had a chronic disease, the more likely the chronic disease has damaged a person’s health and ability to fight infections.
Preventing and reversing chronic disease is possible. Stopping time or being immortal is rather difficult, if not impossible, so if the duration and severity of chronic disease burden has a significant impact on increasing our risk for severe COVID-19, is there a way for us to prevent and/or reverse certain chronic diseases like heart disease, diabetes, and certain cancers? Thankfully, there is strong scientific evidence that through healthy lifestyle behaviors, particularly what we eat, we are able to prevent plaque formation in our arteries, make our body sensitive to insulin again, improve asthma and lung function, and even, reduce cancer formation in our body.
The COVID-19 pandemic has forced us to shelter-in-place, slow down, and reflect on our health. We as a global society are now focused on saving those that are dying from the COVID-19 pandemic and to prevent the 1% of deaths from spiraling any higher. This can happen with each of us doing our part in slowing the spread by social distancing, washing our hands properly, and taking steps to prevent and/or reverse chronic disease to reduce the risk of succumbing to severe COVID-19.
Let food be thy medicine and medicine be thy food — Hippocrates
Disclosures: Views and opinions are my own. As of this published story date, I was an employee of Vir Biotechnology, Inc. and owned shares in biotechnology and CPG companies.