reporter: with duncan in dallas and ashoka mukpo in nebraska both on the same experimental drug, they explain the new drug has never been tested on humans so its effectiveness is unknown. but right now it is their best option in fighting ebola. the enemy is ebola. not people, not countries, not communities. reporter: the pentagon committed to protecting americans on their plans of fighting the deadly disease at its source in west africa with thousands of u.s. troops and hundreds of aid workers. back in texas, a vigil for answers with civil rights leader the reverend jesse jackson while duncan s son prays for his family. his mother in quarantine and his father fighting for his life. i keep praying that my family is okay and my dad will make it out safely. reporter: as for duncan, officials say he s still the only person here sick with the virus with his closest contacts, including his family, still not showing any symptoms. elizabeth herr, abc news,