Because of global warming, glaciers and permafrost are melting, releasing bacteria and viruses that have been trapped inside the ice for years.
Researchers from the French National Centre for Scientific Research, led by microbiologist Jean-Marie Alempic, revived 13 such amoeba viruses known as zombie viruses.
French scientists have revived a 48,500-year-old zombie virus that had been buried beneath a frozen lake in Russia.
The oldest, the Pandoravirus, was found in a lake beneath the surface in Yukechi Alas, Yakutia, Russia.
This has broken the previous record held by a 30,000-year-old virus discovered by the same team in Siberia in 2013.
Other viruses also have been found in the intestines of a Siberian wolf, mammoth fur as well
What is a zombie virus?
The phrase "zombie virus" refers to viruses that have remained dormant for a very long time.
According to studies, old frozen viruses that awaken after lying dormant for years can threaten the public's health.
After studying the live cultures, researchers found that all "zombie viruses" have the potential to be contagious and hence represent a "health concern."