The flu virus is easily passed from one person to the next.
Every year, 5 to 20 percent of the American population catches a flu virus.
Symptoms are similar to those of the regular flu virus.
He became the first American to isolate human flu virus.
More recently, flu virus was isolated from a child in Colorado.
Most cold and flu viruses are spread by direct contact.
These medicines have not worked against most types of the flu virus.
Flu viruses change quickly, so each year scientists make a new vaccine.
"Some types of flu virus are just more deadly than others," he said.
They also stand a greater risk of catching the flu virus, so if you think you've got it - try to avoid them.
