This fits the spread of ebola. It doesn’t need to mutate.
“A more appropriate question might be how long can a virus stay airborne? This can be answered if the size of the specific viral organism is known and how much weight it has to affect the ability of the respiratory droplet containing it to stay afloat on air currents produced by the cough or sneeze. Usually, especially for cold and flu viruses, this is only a matter of seconds and for a diameter of six feet from the person who coughs or sneezes and produces the respiratory droplets, otherwise, they fall from the air to land on surfaces in that approximate 6 foot area.”