Casava Mosaic Virus

Like people, plants can be victims of viruses. They can also be killed by bacteria and fungi.

It happened in Ireland in the 1840's when a water mold caused the Irish Potato famine. One million people died and even more emigrated to countries like the US, which changed our history and culture.

Now an epidemic of a plant virus may do as much damage, if not more. It's called the brown streak virus, and infects the Cassava plant. You may know the crop as yucca, manioc or tapioca. And it feeds 800 million people across Africa, South America and Asia.

Cassava, like potatoes, is grown for its large starch-filled roots, which provide calories though little protein. They're popular in Africa because they're hardy and stay viable in the ground for three years – even through drought.

This helps to stave off starvation when other crops fail.

So you can imagine the impact of the brown streak virus, which is now ravaging cassava crops around Lake Victoria, threatening millions of East Africans. Infected roots, riddled with necrotic brown lumps, are inedible.

Though the virus isn't new, a mutant version emerged in Africa's interior in 2004 and spread like a flu pandemic. The fear is that it'll cross into Nigeria, the world's biggest Cassava grower, because farmers sell cuttings of the plant to one another, in order to start new crops.

It's less likely the virus will cross the ocean into Indonesia, Brazil, or China because there is no world trade in the cuttings. However, white flies, which may spread the virus, could stow aboard planes.

Right now, no cassava strain in Africa is immune to brown streak.

So, farmers are learning to recognize diseased crops and to burn them.

Ultimately, either a strain of Cassava resistant to this virus or a new farming technique will have to be developed to break the infectious cycle.

So, African farmers are learning to recognize diseased crops and to burn them. Ultimately, either a strain of Cassava resistant to this virus or a new farming technique will have to be developed to break the infectious cycle.