Many experts have said they expect COVID-19 to eventually become an endemic disease. There are several key factors that will shape the transition to endemicity on a global scale. However, according to some scientists, the word “endemic” has become one of the most misused of the pandemic. Many assumptions are being made when using this concept, leading to what some are calling misplaced complacency.
For epidemiologists, an endemic disease is one whose overall infection rate is static. This means that the number of people falling ill balances out what is known as the virus’s basic reproduction number. This also includes the number of individuals each infected person passes the virus on to.
In other words, a disease can be endemic, widespread and deadly all at the same time. Malaria killed more than 600,000 people in 2020. Ten million fell ill with tuberculosis that same year and 1.5 million died. These statistics show that endemic disease status does not mean that evolution has somehow tamed a pathogen so that life simply returns to normal.
Thus, the expectation that COVID-19 will become endemic essentially means that the pandemic will not end with the virus disappearing. Instead, enough people will gain immune protection through vaccination and natural infection to mean there will be less transmission and consequently fewer COVID-19-related hospitalizations and deaths, even as the virus continues to circulate.
The expected continued circulation of COVID-19 stands in contrast with the first round of SARS in 2003 and with the Ebola virus outbreak in West Africa in 2014, when public health measures ultimately stopped the spread and brought both outbreaks to an end. These were both global in terms of spread, though not as serious as COVID-19. Importantly, while there are differences between the viruses and the contexts, the comparison conducted by epidemiologists underscores the critical need to improve global public health infrastructure and surveillance systems to monitor for and help respond to the inevitable next potential pandemic virus.
Since viruses spread where there are enough susceptible individuals and enough contact between them to sustain the spread, it is hard to anticipate what the timeline will be for the expected shift of COVID-19 to its endemic stage. There are dependent factors, such as the strength and duration of immune protection from vaccination and natural infection, our patterns of contact with one another, and the transmissibility of the virus.
The conversion of COVID-19 to endemic status is likely to differ considerably from what we have seen with other pandemics because of the heterogeneous responses around the world, with some places engaging in “zero-COVID-19” policies and others having limited or no restrictions, while the variable vaccine availability and uptake is another factor.
While waiting for the endemic stage, we can start to reevaluate what global health professionals want to do about other preventable diseases and health security. We are in the midst of a wave of what specialists call respiratory syncytial viruses that not only include COVID-19, but also the common cold and flu-like symptoms that can be much more severe in infants, the elderly and those with respiratory conditions. On a global scale, tuberculosis and malaria remain scourges that cause suffering. In other words, we have a unique opportunity to think about health policies that are all-encompassing in terms of respiratory infections.
The shift from pandemic to endemic is also psychological, as the mental satisfaction that people may be looking for in terms of a clean endpoint to the pandemic will be missing. Instead, societies will have to adapt to living alongside COVID-19. An endemic disease does not mean it is unmanaged. Rather, what is needed is a shift from viewing COVID-19 as a one-time threat to seeing it as a part of everyday life that we must learn to endure.
There is no doubt that past pandemics have led to massive changes in the way humans live and that we have come to accept them as normal. Some scientists argue that screens on our doors and windows have helped keep out mosquitos that carry yellow fever and malaria, and that sewer systems and access to clean water have helped eliminate typhoid and cholera epidemics. The lessons learned from the COVID-19 pandemic in terms of disease prevention can yield similar long-term improvements in individual and global health.