COVID-19 officially became a pandemic on March 11, 2020. The World Health Organization (WHO) had been closely monitoring this novel coronavirus since early January, when a cluster of pneumonia cases in Wuhan, Hubei Province, China was reported. Past experiences with infectious respiratory viruses such as SARS and MERS informed decision-making in the weeks that preceded the declaration of a public health emergency. Two factors were of high concern: spread and severity. These concerns proved to be more than justified.
As of June 17, 2020, more than 8,000,000 cases of COVID-19 infection have been confirmed globally, and at least 440,000 deaths have been reported. COVID-19 has provided us with the opportunity to examine emerging data in real time. By tracking the history of the infection, it quickly became clear that there are significant differences among people in terms of both risk to infection and — if infected — severity of disease.
The Lancet, a highly respected professional journal, published the first international medical report about COVID-19 infection in Wuhan, China on February 15, 2020, and this article indicated that the infection was associated with acute respiratory symptoms and many other complex medical problems. A March 2020 follow-up study, also in Lancet, discussed the clinical course of the infection and risk factors associated with mortality. Specifically, they looked at how comorbidities (preexisting health conditions) might increase the risk for COVID-19 complications. The researchers noted that older age, hypertension, obesity, and diabetes were all associated with increased disease severity. As the virus spread, so too did support for this finding. From Seattle to New York, patients with COVID-19 did worse when comorbidities were present.
Thankfully, there is some positive news. Among people with COVID-19, it appears that less than 20% become seriously ill, and for those who do experience severe symptoms, the majority seem to fully recover. Outliers — patients who follow no established trend — have also been noted. The wide range of possible outcomes has created anxiety for both the public and the medical community alike. Why do some people fare so poorly while others have only mild symptoms? The answer may be tied to the functional status of an individual’s immune system.