There are 21 known serotypes and infection is spread horizontally between birds.

This selective pressure resulted in the development of processes allowing the viruses to spread horizontally throughout the population.

In recent years, the strike zone had spread horizontally.

Now fame is spread horizontally, across instantaneous electronic networks, rather than deeply, over time.

When the roots spread horizontally, they are able to cover a wider area for collecting nutrients.

And as they made themselves watch, a line of shimmering light suddenly appeared, spreading horizontally before them.

The interface features icons that are spread horizontally across the screen.

Root: Thick central taproot which grows deep and spreads horizontally.

A 'ground cover' layer of edible plants that spread horizontally.

Built low, but it spread horizontally over acres.