In countries and regions that have been under strict lockdowns to stop the spread of the coronavirus, an unintended consequence is visible from space. As businesses, industrial sites and factories closed, and cars and trucks stayed off the roads, the amount of pollution being generated in countries like China and Italy dropped dramatically.

Satellite footage shows a dramatic reduction in air pollution over China and Italy between December 2019 and March 2020 amid the #coronavirus outbreak pic.twitter.com/lweAzUU7i3 — CBS This Morning (@CBSThisMorning) March 19, 2020

Images from the European Space Agency's Copernicus satellite, released on Thursday, show that nitrogen dioxide emissions — a serious air pollutant and a powerful warming chemical — fell by 40% over Chinese cities between December 20 and March 16.

"As nitrogen dioxide is primarily produced by traffic and factories, it is a first-level indicator of industrial activity worldwide," Josef Aschbacher, ESA's director of Earth Observation Programmes, said in a statement. "What is clearly visible is a significant reduction of nitrogen dioxide levels over China, caused by reduced activity due to COVID-19 restrictions, but also the Chinese New Year in January."

The initial drop shown in the animation coincided with Lunar New Year celebrations, a national holiday in China which usually sees a drop in emissions each year. But this year's decline lasted longer than usual as authorities imposed lockdowns to contain the virus.

NASA Earth Observatory images, based on data from the European Space Agency's Copernicus satellite, show nitrogen dioxide emissions dramatically reduced over central China as the coronavirus outbreak brought cities to a standstill. NASA Earth Observatory

"This is the first time I have ever seen such a dramatic drop-off over such a wide area for a specific event," NASA air quality researcher Fei Liu said on NASA's Earth Observatory blog.

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Italy, which has now exceeded China as the country with the most deaths from coronavirus, has been under an emergency nationwide lockdown since March 9. It has also recorded a significant drop in nitrogen dioxide emissions related to reduced auto traffic and industrial activity.

Satellite images show that the most dramatic decline of air pollution was observed over northern Italy, the first region in the country to go on lockdown.

As of Friday, the pandemic has killed more than 11,000 people worldwide and the number of confirmed COVID-19 cases is rapidly climbing. There are more than 16,000 confirmed cases in the United States and over 258,000 cases globally, according to data compiled by Johns Hopkins.

China's health ministry says the city of Wuhan — the original epicenter of the coronavirus pandemic — and the surrounding Hubei province reported no new cases in the last 24 hours, providing hope in the global fight against the virus.