As the Covid-19 pandemic disrupts the lives of billions around the world, two questions continue to linger: Where did the virus come from, and how did it find its way into humans?
Scientists have been hunting for those answers since the first cluster of unusual pneumonia cases emerged in China in December 2019. Investigating the origin of the novel coronavirus is a daunting task that can be compared with assembling a difficult jigsaw puzzle with most of its pieces missing. But mapping out the virus’s spread is of crucial importance to prevent new epidemics. Discovering where the virus came from could teach scientists and leaders how to avoid the situations where viruses are most likely to be introduced into humans.
The initial puzzle pieces of the Covid-19 pandemic were put together when whole genome sequencing of the virus showed that it shared 79.5% of its RNA with SARS-CoV, the coronavirus that had been responsible for the 2003 SARS outbreak, and was even more similar (96.2% identical) to another coronavirus called RaTG13, which had been previously found in a bat. This strongly suggested that the newly identified SARS-CoV-2 also came from bats.
Some of the earliest cases of Covid-19 were connected to a local seafood market in the city of Wuhan, which seemed to indicate that the market was where the virus made its leap from the winged mammals to humans. But it soon became clear that not all of the early cases could be traced back to the market. Only 66% of the initial 41 patients had been exposed to the location. Notably, the first patient identified (who is not necessarily the first to have acquired the disease) had not been to the market.
Patient zero: a fruitless quest?
At that point, the quest to find the very first person who came down with Covid-19 — the pandemic’s “patient zero” — became quite an unrealistic endeavor, according to scientists. With the majority of people infected with Covid-19 suffering from mild symptoms or no symptoms at all, the virus could have been circulating silently in the population before it garnered the…