The nation’s top public health agency has stirred confusion, by posting — and then taking down — an apparent change in its position on how easily the coronavirus can spread through the air. Officials at the Centers for Disease Control and Prevention say the respiratory virus spreads primarily through small airborne droplets. CDC officials have also acknowledged growing evidence that the virus can also be carried on smaller, aerosolized particles that spread over a wider area. The agency’s position appeared to have changed when it posted new detail on aerosolized particles on Friday, but that language was removed on Monday.