Dave's ESL Cafe's Student Discussion Forums

[tisogai]

Dear Teachers,

Please help me understand what the underscored part mean.

The rain forests are also its largest reservoirs of viruses, since all living things carry viruses. When viruses come out of an ecosystem, they tend to spread in waves through the human population, like echoes from the dying biosphere.

Will you please rewrite the part for me to be able to understand it.
Thanks so much.

[pugachevV]

To spread in waves here means that it passes through the human population as waves pass through the sea, or ripples emanate from a stone dropped in a pond.
Like echoes from the dying biosphere... A biosphere is a region on the surface and atmosphere of the earth occupied by living organisms, so this writer is trying to say that as the rain forests are destroyed, so the viruses they contained are set free to roam through the human population.