In 2014, a team of French scientists made a remarkable discovery when they successfully reactivated a virus known as Pithovirus sibericum, which had been frozen in Siberian soil for over 30,000 years. The virus was identified by researchers from the Laboratoire information génomique et structurale in Marseille, led by Jean-Michel Claverie and Chantal Abergel. The frozen soil sample was collected from the tundra of Chukotka, a region near the Sea of Siberia, where the average annual temperature is around -13.4°C. Radiocarbon dating confirmed that the soil was from a time when mammoths and Neanderthals lived on Earth. Pithovirus sibericum is a large virus, measuring 1.5 micrometers in size—about one-thousandth the width of a human hair. It specifically targets amoebas, which are single-celled organisms, and poses no threat to humans. The virus’s name comes from its shape, which resembles an ancient Greek amphora, or jar, with "pithos" being the Greek word for a jar. Unlike many viruses, it can be observed using a regular optical microscope, not requiring the more powerful electron microscope. In the lab, the virus was thawed and shown to replicate by infecting amoebas, ultimately killing them—a clear sign that the virus was still biologically active after millennia in the ice. The researchers chose amoebas as a test subject deliberately. According to Chantal Abergel, the viruses they study are selected for their lack of danger to humans. Amoebas act as a biological indicator, helping scientists detect active viruses without handling pathogens that could affect humans. This method allows for safe study of viruses that might otherwise be too hazardous to handle directly. The discovery challenged previous assumptions about the effects of freezing on viruses. It was once believed that freezing would destroy or render viruses inactive for long periods. However, Pithovirus sibericum remained infectious even after 30,000 years in permafrost, quickly infecting amoebas in the lab once exposed. This is not an isolated case—another giant virus, Mollivirus sibericum, was also isolated from the same permafrost sample in 2015. These findings raise questions about the potential risks of thawing permafrost, whether due to climate change or human activity in Arctic regions. Jean-Michel Claverie suggested that if such viruses can remain active, then diseases like smallpox might not be completely eradicated from the planet, but this remains a hypothesis rather than a proven fact. Since the discovery of Pithovirus sibericum, other members of the Pithoviridae family have been found in permafrost. In 2016, a similar virus called Pithovirus massiliensis was discovered in a wastewater sample in southern France. This suggests that these viruses are not only preserved in ancient ice but also continue to exist in more common environments, highlighting their resilience and ongoing presence in the natural world.