Viruses are an organism that is at the edge of life itself. It’s hard to say if they are living or non living. Some of them can be dead for hundreds of years before entering a host and becoming alive. There are more than 5000 virus species known to man. Some of these have been eradicated by science while others keep evolving into new strains that are harder to fight. And for some we just have no known cure. Here we go with top 10 deadliest viruses known to science.