The COVID-19 pandemic may be over, but questions about its origins still baffle scientists. There are many theories on where SARS-CoV-2 could have come from, but there's no definitive proof to back any of them up.

One of the biggest questions that came with the COVID-19 pandemic was: Where did the virus come from? Three years went by not so quickly as the world struggled with containing the disease, but experts still haven't found the answer to that question.

In the earlier days of the pandemic, there was a general notion that SARS-CoV-2 came from bats. But there's no evidence to prove this. The only thing that's been made clear is that COVID-19 is zoonotic, which means it's a human disease of animal origin, according to Bat Conservation Trust.

While the idea that the virus originated in bat species does not seem far-fetched, scientists believe that there must have been an intermediary species that brought the virus from bats closer to humans. Through mutation, the virus was able to transmit from person to person, leading to the global health crisis that started in late 2019.

Another theory claimed that carelessness at a laboratory in Wuhan, China, could have resulted in the spread of the novel coronavirus. The idea gained more traction when several news outlets reported about the lab studying bat viruses.

There was also a story on how the virus started spreading from infected wildlife sold at a Chinese market. But then again, no one was able to find solid evidence to back this up.

Scientists have struggled to find conclusive proof that would point to the geographic and biological origins of COVID-19, prompting Reuters to say this week that we may never really know where SARS-CoV-2 came from even when the pandemic is already deemed over.

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Aside from the lack of evidence, there's also been an issue with how China censored pertinent scientific data to the rest of the world. By withholding important information, the rest of the world will only rely on speculations that are hard to prove.

"We continue to call on China to be transparent in sharing data and to conduct the necessary investigations and share the results. Understanding how the pandemic began remains both a moral and scientific imperative," World Health Organization Director-General Tedros Adhanom Ghebreyesus said in March.