A new video by researchers in the U.K. shows a virus infecting cells in a lab faster than previously thought possible.

Scientists at the Imperial College London filmed the spreading virus under a microscope and say that understanding this rate of infection could lead to new drugs to stop viral diseases.

Normally, a virus spreads by entering a cell and co-opting the machinery of the cell to make copies of itself. The viruses then burst out of the cell to infect more cells, with speed limited by how fast the virus can replicate.

In a study published this week in Science, however, scientists found that vaccinia viruses, used in the vaccine that eradicated smallpox, can spread four times more quickly that thought possible.

"This fundamentally changes how we think about virus dissemination and similar strategies may very well be exploited by many viruses," said Geoffrey Smith, a virologist at Imperial College London, in a statement.

The video shows viruses infecting live monkey liver cells growing in a culture.

The researchers think the virus is spreading quickly by bypassing cells that are already infected and moving on to uninfected cells as quickly as possible.

After a vaccinia virus infects a cell, it causes two proteins to appear on the cell's surface, marking it as infected, the scientists found.

Gets them to move on

When more viruses approach the infected cell, snake-like projections formed by the virus inside the cell, called "actin tails," emerge from the cell's membrane and repel the viruses.

The viruses keep getting pushed around by these tails until they reach a cell that hasn't been infected.

"Thus the virus can spread quickly to distant uninfected cells without needing to replicate in each cell on the way," said Smith.

In another experiment, the researchers prevented the viruses from making the actin tails, and this slowed how fast the virus could spread.

The authors of the study say this mechanism could explain why some viruses, such as herpes simplex, spread faster than the speed of their replication would allow.

It also could lead to new drugs that stop viruses from spreading using this mechanism.

"Understanding how viruses spread is fundamental to designing strategies to block spread and thereby prevent disease," said Smith.