Transcript for Counting cars: Satellite images suggest coronavirus may have hit China last fall
Back now with an exclusive investigation into the origins of the coronavirus. Researchers tracked down new evidence showing what could be an even earlier appearance in China and our chief national affairs correspondent Tom llamas is here with the findings. Good morning, Tom. Reporter: George, good morning to you. China has come under scrutiny for its initial response to the coronavirus and as we've learned here and around the world time is of the essence when battling this deadly disease. What you're about to see is the doctors who are disease specialists found in Wuhan and leading to more questions. This morning, new evidence the coronavirus may have been sweeping through Wuhan long before Chinese health officials told the world they had a problem. These satellite photos seen here for the first time show various Wuhan hospitals on several days in October of 2019. The clues are all those red dots. They represent cars inside packed hospital parking lots. Three months before the Chinese government announced the spread of covid-19. When you start pulling these images together and see a pattern emerge the first thing you think of there's no way it could be possible. Reporter: This doctor is the lead researchers. He specializes in disease available. Using images from commercially available satellites, he and his team analyzed more than 300 photos of Wuhan hospital. Satellite photos mirror images, October 2018, October 2019 and you see the number of cars skyrocket. So much greater and greater than any other sort of time period that we had looked at through multiple years. Reporter: This satellite image of hubei women & children hospital was taken in October of 2018 with 393 cars in the parking lot. A full year later, 714. At Wuhan's tianwow hospital, it jumped from 171 to 285 cars. 112 compared to 214 a year later at tongji medical university. Maybe infection is growing and people have to see a doctor. Reporter: Researchers say they can't prove this increased activity is due to covid-19, but they did uncover another clue when they looked at the Google equivalent in China. You looked into the internet searches of what was happening in October. What did you find? We found people were searching for terms related to diarrhea, which we know now is important symptom of covid-19 as well as cough and these were starting to increase, you know, late summer and early fall. Reporter: Brownstein says he considered potential outside factors unrelated to coronavirus that could impact this spike like mass gatherings or natural disasters. We looked through all this and couldn't identify any other reason for this signal. Reporter: ABC spoke with multiple infectious disease experts who told us there's almost always a delay in identifying and then reporting an outbreak. China has adamantly maintained they reported the outbreak in a timely fashion. But their own CDC director recently told Chinese local media the novel coronavirus had existed long before it was found at the wet market in Wuhan in late December. Now, we have asked the Chinese government for reaction to these photos and the research. They had no comment but they did point us to a statement they put out yesterday that said, quote, the origin of the virus requires research and must be based on facts and evidence. George. Fascinating, Tom llamas, thanks very much.
This transcript has been automatically generated and may not be 100% accurate.