Understanding the Shift of SARS-CoV-2 to an Endemic State
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Chapter 1: The Path of SARS-CoV-2
The COVID-19 pandemic has changed our lives dramatically. Back in February, then-President Trump optimistically stated that the coronavirus would simply vanish one day, likening it to a miracle. Fast forward nearly eight months, and we find ourselves grappling with rising infection rates nationwide, escalating from approximately 35,000 daily cases last September to over 250,000 in January. The reality is clear: this virus is here to stay. However, there is a silver lining; vaccination efforts are progressing, and humanity has navigated similar challenges in the past.
As the pandemic continues, some areas may already be experiencing endemicity with the SARS-CoV-2 virus, which refers to diseases that are “consistently present within a specific population or geographic area.” An epidemic arises when a disease spreads within a particular group, while a pandemic is characterized by widespread transmission across multiple populations. Both scenarios involve a new infectious agent that the human immune system has not encountered before. Conversely, an endemic infection is when the same pathogen persists in a community but no longer causes the severe consequences it once did.
For instance, chickenpox is an endemic disease in the U.S., and many sexually transmitted infections, such as syphilis, are endemic globally. Certain diseases, like malaria, have coexisted with specific populations for so long that genetic mutations—like the sickle cell trait—have emerged, providing some individuals with protection against severe outcomes. In Africa, where malaria is prevalent, a significant percentage of those affected also carry the sickle cell trait, showcasing how communities have adapted to living with these diseases.
The original strain of the flu that emerged in 1918 still exists today, but it no longer poses the same threat as it once did.
Section 1.1: Evolution of Pandemics
How does a disease transition from a pandemic or epidemic to an endemic state? For this evolution to occur, several conditions must be met: the disease must be transmitted from person to person, it cannot be entirely lethal, and each infected individual must pass the virus to at least one other person, but not in overwhelming numbers. This pattern typically follows a period of developing immunity within the population. If a community lacks immunity, the virus can proliferate unchecked, leading to an epidemic.
Eventually, an infection that starts as an epidemic or pandemic will either dissipate or stabilize at a low transmission level, effectively becoming endemic.
How Does Covid-19 Become Endemic?
This video delves into the mechanisms behind COVID-19's potential transition to an endemic state, exploring past pandemics for context.
Section 1.2: Historical Context of Endemic Diseases
Examining historical endemic diseases reveals that they were not always the mild inconveniences we recognize today. Initially, these diseases often had devastating impacts. The 1918 influenza pandemic, for instance, infected around 500 million people and resulted in approximately 50 million deaths globally, marking it as one of history's deadliest pandemics. It persisted for nearly two years, concluding in the summer of 1919—not due to a vaccine, which was not developed until 1942, but because those infected either succumbed or developed immunity.
Influenza remains a threat today, mutating continuously and necessitating new vaccines annually. However, the original strain from 1918 persists in a less virulent form.
As we observe the SARS-CoV-2 virus, signs suggest it may be undergoing a similar transformation. Like influenza, it spreads through the air and from person to person. Certain regions where the virus peaked are now witnessing a decline in cases. For example, North Dakota, which saw a spike in mid-November, is now experiencing a downturn. In contrast, California, which faced a minor peak in July, is currently seeing a resurgence. Patterns like this are evident across various states.
In my experience as an ear, nose, and throat (ENT) physician in New York City, I have witnessed these trends firsthand. While overseeing COVID-19 compliance for major television productions, we conducted extensive testing. Over three months, only one individual tested positive, and that person had traveled from an area yet to experience a peak.
Ultimately, this pandemic will either fade away or evolve into an endemic state.
Endemic: The Next Covid-19 Phase, Explained
This video discusses the potential future phases of COVID-19, focusing on its transition to an endemic phase and what that means for society.
Despite the uptick in COVID-19 cases, this trend is primarily observed in regions that have yet to experience a peak. In New York City, where the virus has been present since January and hit hard initially, we are starting to see evidence of declining hospitalizations and fatalities, even as testing rates rise.
Although the infection rates in New York City are not as high as they were last spring, SARS-CoV-2 remains present. Given its airborne nature, we must recognize that not just individuals but entire locations can be exposed to the virus. Even with robust social distancing and mask-wearing efforts, virus transmission is still a concern in enclosed spaces.
As we await widespread vaccination, it's possible that SARS-CoV-2 is already becoming endemic in various regions. Given that nearly eleven months have passed since New York City's first infection, one must wonder if it is time to stop labeling it as "novel." Ultimately, this pandemic may either diminish or transition into an endemic phase. While many hope for its eradication, the evidence suggests that the latter may already be occurring.