he coronavirus that conquered the world came from a thumb-sized bat tucked inside a remote Chinese cave. Of this much, scientists are convinced.

Exactly how and when it fled the bat to begin its devastating flight across the globe remain open questions.

In just one year, SARS-CoV-2, the virus that causes COVID-19, has infected 100 million people and killed 2 million, 400,000 of them in the U.S. Answers could stop such a calamity from happening again.

Researchers in China, under government scrutiny, have been investigating since January. This week, a World Health Organization delegation of scientists from 10 different nations finally was allowed in the country to explore the virus’ origins.

“This is important not just for COVID-19, but for the future of global health security and to manage emerging disease threats with pandemic potential,” Tedros Ghebreyesus, WHO’s director-general, said just after the team left for China.

It’s not clear how much evidence will remain a year later, and what the team will be able to learn. The Wuhan fish market, seen as a likely breeding ground for the virus, has been scrubbed and shuttered.

But the effort is worth it, infectious disease experts say. Understanding the journey of SARS-CoV-2 may provide insights into how the relationship between humans and animals led to the pandemic, as well as other disease outbreaks including Ebola, Zika and many strains of flu.

“These are emerging diseases that breach the barrier between animals and humans and cause devastation in human populations,” the WHO’s Mike Ryan said at a Monday news conference. “It is an absolute requirement that we understand that interface and what is driving that dynamic and what specific issues resulted in diseases breaching that barrier.”

The international team is not looking to assign blame, said Ryan, executive director of WHO’s Health Emergencies Programme. If it were, there would be plenty to go around.

“We can blame climate change. We can blame policy decisions made 30 years ago regarding everything from urbanization to the way we exploit the forest,” he said. “You can find people to blame in every level of what we’re doing on this planet.”

Beginnings in a cave
The chain of events that led to the worst global pandemic in a century started with a tiny, insect-eating mammal with the mundane name, Intermediate Horseshoe bat.

The species is part of a family of bats that act as natural reservoirs for coronaviruses, notorious for how easily they mutate and how well they can be transmitted from species to species. The bats aren’t bothered by the viruses. The animals they pass them onto aren’t always so lucky.

Humans are one of those animals.

This happens all the time – a virus harmlessly infects one creature then finds its way to another, mutates and becomes something new. The newly mutated virus can be insignificant but annoying (think common colds, some of which are caused by coronaviruses) or devastating and deadly (think smallpox.)

SARS-CoV-2 is a little of both.