Earlier today, the first Ebola patient to have been diagnosed within the US died of his infection. Thomas Eric Duncan succumbed to his illness 11 days after being admitted to the hospital. Duncan had become infected while in Liberia, but was asymptomatic until after his travels brought him to Dallas, Texas.

Also in Dallas, a sheriff's deputy has been hospitalized after exhibiting a limited set of the symptoms that are used to diagnose Ebola infection. The deputy had been in contact with some of Duncan's family members, but not the infected individual. CNN quotes an official from the Centers for Disease Control as saying that the individual, "does not have either definite contact with Ebola or definite symptoms of Ebola." Nevertheless, a local hospital has admitted him through its emergency room as a possible case of exposure.

In response to these events, the US has announced that passengers arriving from three countries where the epidemic is uncontrolled—Guinea, Liberia, and Sierra Leone, will be subjected to screening if they arrive in any of five major airports. (These are JFK, Dulles, Newark, Chicago O'Hare, and Atlanta's Hartsfield-Jackson.) Customs staff will observe them, ask basic health questions, and screen them for fever. This will supplement the existing exit screening procedures already in place in the affected countries.

The White House notes that this exit screening hasn't identified anyone infected with Ebola, although it has successfully caught a few cases of malaria.