U.S. Will Restrict Travel From Ebola-Hit West African Countries to 5 Airports

The Department of Homeland Security announced Tuesday that airline passengers traveling to the United States from the the countries most affected by the Ebola outbreak must travel through one of five U.S. airports, where they will undergo screening.

The new restrictions take effect Wednesday and expand on a previous requirement that passengers whose travel plans originate in Liberia, Guinea and Sierra Leone must undergo screening if they arrive at airports in New York, Newark, Washington, Atlanta or Chicago. Now, passengers must modify their itinerary to ensure they arrive at one of the five airports where they can be screened.

Though the tighter security measure is symbolically significant, it will likely only impact a small minority of travelers who arrive in the U.S. from West Africa. More than 9o% of passengers from the affected countries already arrive at those five airports via air connections in Europe or elsewhere in Africa. There are currently no direct flights from Liberia, Guinea or Sierra Leone to the U.S.

In a statement, Homeland Security Secretary Jeh Johnson said that the agency would continue monitoring the situation to determine whether additional restrictions are necessary.

See The Tobacco Leaves That Could Cure Ebola

Tobacco plants are grown for six weeks in the Medicago greenhouse in Quebec City so their leaves are large enough to serve as a factory for making antibodies. The plants are not modified or genetically altered in any way during this time.

Mathieu Belanger—Reuters

Researchers at Icon Genetics in Germany prepare the DNA coding for antibodies that can neutralize Ebola. These genes are inserted into a soil bacterium that easily infects the tobacco plant cells. Once in the cells, the gene is treated like any other plant gene and the plant starts churning out the antibodies.

Sean Gallup—Getty Images

To infect the leaves with the antibody-containing bacteria, the plants are submerged in a water solution of the loaded bacteria. Plant cells have plenty of empty spaces filled with air, so a vacuum removes the air and the water, along with the bacteria and antibody genes, flow in.

Mathieu Belanger—Reuters

The leaf at the bottom has not been treated. The leaf on top is now an antibody-making factory. The plant's normal machinery starts making the antibody as if it is a plant protein.

Mathieu Belanger—Reuters

Researchers at Icon Genetics grind the leaves down to filter out the antibodies.

Sean Gallup—Getty Images

Ultraviolet light reveals the clusters of cells that are busy making antibodies. One kg of leaves produces about 5g of antibodies, which is about a third of the dose required to treat an Ebola patient.

Sean Gallup—Getty Images

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Write to Justin Worland at justin.worland@time.com.