A microscopic representation of a virus
M. chilensis surpasses any DNA virus ever seen before.

The world's largest virus has been discovered in the sea off of Chile, harbouring more than 1,000 genes.

Researchers have said the Megavirus chilensis has a genome 6.5 percent larger than the previous virus record-holder, Mimivirus, isolated in 2003.

Like the Mimivirus, the new isolated virus thrives in freshwater amoebae, single cell organisms.

Viruses are usually far smaller than bacteria and need to penetrate a host cell to replicate.

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The Megavirus is 10 to 20 times longer than average and is even longer than some bacteria. It is genetically the most complex DNA virus ever described, but its host organism is not yet known.

"It is bigger than some bacteria," said Professor Jean-Michel Claverie, from Aix-Marseille University, Marseille, France. "You don't need an electron microscope to see it; you can see it with an ordinary light microscope."

Unile many DNA viruses like pox or herpes, Megavirus chilensis "doesn't seem to be harmful for humans," he said.

The scientists discovered the virus when they were sampling sea water near a marine station in Las Cruces, Chile. The study appeared in the U.S. journal Proceedings of the National Academy of Sciences.