A primary reason is that viruses do not possess a cell membrane or metabolise on their own - characteristics of all living organisms. Examples of common human diseases caused by viruses include the common cold, the flu, chickenpox and cold sores.
In the past spacecraft have taken greatly different amounts of time to make it to Saturn. Pioneer 11 took six and a half years to arrive. Voyager 1 took three years and two months, Voyager 2 took four years, and the Cassini spacecraft took six years and nine months to arrive. The New Horizons spacecraft took a short two years and four months to arrive on the scene.
It took total of 5 days, 22 hours and 54 minutes to fly to the Moon and return back to Earth. The shortest trip to the Moon took place in January 2006 by the NASA Pluto probe New Horizons. With the speed of 58,000 km/hr, it only took 8 hours and 35 minutes to get to the Moon from Earth. The longest trip took place in 2003 by the ESA SMART-1 lunar probe.