With 2 ½ years of COVID-19 experience behind us, we can now identify the missed opportunities the medical and public health communities had to control the pandemic. There are three well-established areas where the virus caught the world unprepared: asymptomatic viral transmission from the infected to the uninfected; airborne spread from extremely small particles, especially indoors; and rapid emergence of new COVID-19 variants. These unexpected and mostly unprecedented developments thwarted early efforts to control the virus and caused devastating consequences including more than 6.5 million deaths worldwide and counting.
-- Asymptomatic transmission: With its initial community spread, COVID-19 appeared to behave like influenza in early 2020. Gradually a crucial difference between COVID-19 and the flu became apparent. With the flu, the majority of the population has been exposed in previous years to some flu variant, so an immune response and the attendant symptoms — fever, sore throat, runny nose — develop quickly with subsequent infections. So, as the flu virus becomes transmissible, many people are already exhibiting symptoms.
What was unrecognized with COVID-19 was that many infected patients could transmit the virus before showing symptoms. Because this was a new virus that no one had experienced in the past, humans did not have specific immune memory. As a result, those infected did not show symptoms right away. Before people knew they were sick, they were becoming contagious as the virus multiplied in their bodies. The situation is different today because most people have had COVID-19 or have been vaccinated. With that acquired immune memory, they develop symptoms earlier, and those symptoms correlate more closely, but not perfectly, with the potential for viral transmission.
