■ Deciphering the virus’ origin story.

The best minds in virology are trying to unravel a mystery: How did a lethal coronavirus jump from the wilds of rural China to major human population centers? And what chain of genetic mutations produced a pathogen so perfectly adapted for stealth and mass transmission?

Deciphering the creation story of SARS-CoV-2, as the virus now rampaging around the globe is known, is a crucial step toward arresting a pandemic that’s killed 270,000-plus and triggered what could be the worst economic collapse since the Great Depression.

While crash vaccine programs are underway in the U.S., Europe and China, an inoculation to ward off the virus may not be ready for months, and the jury’s out on potential treatments. In the meantime, to reduce the risk of deadly secondary outbreaks or the emergence of an entirely new strain, disease chasers need to retrace the pathogen’s journey around the globe. That means heading back to China, where it all started sometime in 2019.

Last week, the World Health Organization sought permission from Beijing to send a new scientific mission for more epidemiological detective work. China, which let a WHO team into the country in early February as its epidemic raged, hasn’t yet signed off.

President Xi Jinping, who’s personally overseeing China’s virus response and investigation into how the outbreak started, is keeping tight control over Chinese scientific research, which must be approved prior to publication by authorities, according to two people familiar with the situation.

However, as death tolls and joblessness rise worldwide, pressure on Beijing is intensifying to allow international researchers back in to interview survivors, do field work and examine virus samples that the country has been stingy about sharing, according to the U.S.

Nearly half a year into a historic global health crisis, there are still enormous gaps in our knowledge. Those unanswered questions are hampering our ability to contain the outbreak and to prevent future pandemics, while fueling a war of words between the U.S. and China over the origins of the virus.

Roughly 70% of emerging infectious diseases in humans are zoonotic, or transmitted from animals to people. Genome sequencing of SARSCoV-2 shows it’s related to two other deadly coronaviruses that originated in bats.

Severe acute respiratory syndrome, which started in China in 2002, and Middle East respiratory syndrome a decade later spread to humans via a secondary animal source. In the case of SARS, experts pointed to civet cats — small, sleek nocturnal mammals used in wildlife dishes in China — as the probable conduit. With MERS, camels are believed to be the carrier.

It’s presumed that SARSCoV-2 has made a similar journey, yet investigators have yet to identify an intermediate animal host, according to Peter Ben Embarek, a WHO food safety and animal diseases expert.